James Hillier

The Magnetic Electron Microscope Objective: Contour Phenomena and the Attainment of High Resolving Power

A theoretical and experimental investigation of contour phenomena observed in electron microscope images near focus has been carried out. An explanation for the apparent reversal of the Fresnel fringes at exact focus is given and a method is described for the determination of the degree of asymmetry from the fringe patterns. A procedure for empirically correcting the asymmetries usually present in magnetic electron microscope objectives is outlined and some of the results obtained with a compensated lens are shown. A number of instrumental defects which may prevent the attainment of the ultimate resolving power of an instrument, together with methods for their elimination, are listed.

On the Investigation of Specimen Contamination in the Electron Microscope

A number of experiments directed toward determining the nature and cause of deposits which occur on electron microscope specimens under electron bombardment are described. From these the conclusion is drawn that the material is a result of chemical reaction, occurring at any surface simultaneously bombarded by electrons and organic molecules. The organic vapors are shown to arise in two ways: (1) by diffusion out of the metal walls, gaskets, and greases exposed to the vacuum, (2) by the outgassing of metal parts of the instrument exposed to electron bombardment. To eliminate the effect both sources must be removed.

Improved Ultra‐Thin Sectioning of Tissue for Electron Microscopy

The use of a reservoir of liquid to collect ribbons of thin sections as they are cut enables serial sections to be obtained and provides means for detecting variations in thickness. Reducing the effects of static friction and of external vibrations makes it possible to cut long series of sections 0.2μ thick and uniform to better than five percent. Some observations which may throw some light on the mechanics of the cutting process are reported. Mounting the sections without any treatment is shown to be superior to any technique in which the embedding material is removed or replaced. It is shown that the technique provides sections in which a structural resolution of 200A is possible. The remaining artifacts introduced by the sectioning and mounting are easily recognized deformations which do not influence the interpretation.

On the Improvement of Resolution in Electron Diffraction Cameras

An electron optical system is described in which it is possible to obtain (1) high resolution electron diffraction patterns, (2) shadow electron microscope images, and (3) electron diffraction patterns of selected variable areas of the specimen. The change in mode of operation of the system is accomplished by electrical adjustments without changing the specimen position in any way. A number of phenomena related to the attainment of high resolution diffraction patterns are described. Pertinent details of the experimental apparatus are discussed and some representative results are shown.

An Objective for Use in the Electron Microscopy of Ultra‐Thin Sections

An objective has been designed which is particularly suitable for the study of tissue sections. It consists of a large opening polepiece system operated at a focal length of 12 mm. It includes a diaphragm which can be centered (not during operation) and translated on the axis. Angular apertures of as low as 2×10−3 radian with large areas of bright field can be achieved. A simple method of aligning the aperture is described.

A Discussion of the Illuminating System of the Electron Microscope

A practical means for estimating the average performance of an electron microscope is proposed. Some first‐order theory of the operation of an electron‐microscope objective is given to demonstrate the extreme sensitivity of the instrument to the adjustment of the illuminating system. It is shown that by considering the illumination as being produced by a two‐lens system it is possible to explain qualitatively all the effects observed in practice in connection with the illumination of the specimen. Practical information regarding the exact adjustment of the illuminating system is also given. The cause and elimination of multiple images is discussed. Changes in the design of the electron source and the use of an interchangeable aperture in the condenser lens are shown to improve the average performance of the instrument considerably.

A Study of Distortion in Electron Microscope Projection Lenses

The origin of distortion in electron microscope projection lenses is discussed and the serious nature of its effect on the measurement of particle size distributions is pointed out. Methods of measuring distortion are described. By means of first‐order theory it is shown to be possible to correct distortion by the use of a two element projection lens. The degree of correction obtainable is shown to be satisfactory for most practical purposes. A double gap projection lens polepiece and the correction of distortion obtained with it are described.

A Diffraction Adapter for the Electron Microscope

An adapter has been developed which allows a conventional electron microscope to be used interchangeably as an electron diffraction camera or an electron microscope. The adapter comprises a unit which takes the place of the projection lens unit of the microscope, and includes a newly designed microscope projection lens, a specimen holder, and a focusing lens. To transform the instrument from a microscope to a diffraction camera (or vice versa) it is necessary only to transfer the specimen from the regular object chamber to the adapter. Diffraction patterns may be obtained by either reflection or transmission. As a result of the excellent reproducibility of voltages and currents from the regulated power supplies used in the electron microscope, the diffraction camera holds its calibration to within 0.1 percent over long periods. Using a calibration determined by measurements of gold patterns, lattice spacings of a number of common materials were determined and found to agree with x‐ray values to within 0.5...

Light and electron microscopic studies of Escherichia coli-coliphage interactions II. The electron microscopic cytology of the E. coli B-T2 system☆

High contrast electron microscopic observations were made at known intervals after infection of E. coli B cells infected with T2 phage. During the first half of the latent period, marginal vesicular areas replaced the alternating dark and light patterning of normal cells. The latter half of the latent period was characterized by gross changes in the texture of the cytoplasm and by the gradual internal build-up first of phage “Anlagen” and second of mature phage progeny.

A Removable Intermediate Lens for Extending the Magnification Range of an Electron Microscope

A removable intermediate lens is described which extends the range of magnification of a conventional instrument to 25:1 without sacrificing the accessibility of the objective and projection lens polepieces. The distortion, sensitivity to changes in accelerating potential and reproducibility of calibration are studied and found to be equal to, or better than in the standard arrangement. The system provides two values of the magnification which are essentially independent of the accelerating potential.