John H. L. Watson

An Effect of Electron Bombardment upon Carbon Black

A significant change is reported in mean particle size and shape characteristics of carbon black due to specimen contamination while under examination in electron microscopes. The effect is described for a number of well‐known commercial blacks and examples are given in graphical form to illustrate expected variations in mean particle size with continued bombardment at normal focusing intensities. The effect is observed in other materials but is more pronounced in carbon black. Suggestions are made for minimizing the effect.

Pseudostructures in Electron Microscope Specimens

Pseudostructures, which are not real properties of electron microscope specimens but are introduced by the action of the electron beam, are described. Examples are given from samples of tetracopper calcium oxychloride, precipitates from slowly hydrolized ferric chloride solutions, and tungsten oxide to illustrate some of the effects which may occur. The polymorphism of these substances, particularly of tungsten oxide, is discussed.The major effects which contribute to the pseudostructure formation are melting, evaporation, change of crystalline states, increase in degree of crystallinity, and migration of material. Reasons are given for concluding that the primary cause of specimen changes is to be found in the heating effect of the beam. The possibilities of secondary causes are also considered.Artifacts may also be introduced into bacterial specimens. Observed changes in such samples are described briefly and examples are given.

The Reliability of Internal Standards for Calibrating Electron Microscopes

Conclusions important to the practice of electron microscopy are drawn from experiments. Particles of Dow Latex 580G are unstable under electron beams and best micrographed at low intensity. Two different effects of radiation are noted. At low intensity the mean diameter in the present work was 2890A, the standard deviation of the spherical particles was 60A. 580G is improved as an internal standard if recalibrated by some other suitable standard (not the reverse) each time before use. Fresh replicas of diffraction gratings are still the most practical standards, reproducing gratings to two percent. By an independent optical method (spectroscopy) one can measure the grating space of a replica when it is on an eighth‐inch, 200‐mesh specimen screen under exact calibration conditions for electron microscopes. Specific replicas, and from them specific preparations of 580G are checked easily and accurately by the spectroscopic method. Replica age or other factors which may affect accurate reproduction of an or...

Electron Microscope Examination of the Microphysical Properties of the Polymer Cuprene

The microphysical structure of cuprene is described from electron micrographs and some suggestions are made concerning the mechanism of the formation of this substance. Cuprene samples prepared by polymerization of acetylene in the presence of finely divided cuprous oxide are shown to be composed of hollow fibers characterized by both longitudinal and transverse structure. The striking appearance in electron micrographs of this type of cuprene serves to identify it in clogging deposits taken from acetylene lines. This is illustrated by a deposit taken from a reactor used in the process of hydrogenation of acetylene to ethylene. Cuprene specimens formed by alpha‐ray bombardment of acetylene gas are shown to be composed of round particles joined by short, straight, thick necks which are about 500 to 1000A in length. These are samples of cuprene which have been bombarded further by alpha‐particles after their initial formation. An oxidized sample has round particles of mean diameter 4900A; an unoxidized samp...

Filmless Sample Mounting for the Electron Microscope

A method is described for supporting airborne particles upon thin glass fibers where they build up in chains and may be examined in the electron microscope. With no supporting membrane, the contrast and resolution are increased in the micrographs. The specimens are particularly useful for stereoscopic studies. A special reference is made to the study of carbon particles mounted in this fashion. The carbons examined are formed by pyrolysis of acetylene and occur naturally in pronounced chains. Reproducible particle size data for the carbons can be secured by measurements made on individual particles at ×200,000. Evidence for the crystalline nature of this carbon is rendered visible in the micrographs.

Scanning electron microscopy of gastroscopic biopsies

Endoscopic biopsy specimens of normal human gastric mucosa and mucosa in erosive and chronic gastritis were studied by scanning electron microscopy. The orifices of the gastric pits and the cobblestone surface of epithelial cells covered with villus-like and bulbous projections were observed. A possible mechanism for mucus secretion from these cells is suggested. The mucosa showed striking morphologic surface differences from the normal in cases of both erosive and chronic gastritis.

The fine structure of submicron iron particles

SummaryHigh resolution electron micrographs are shown of samples of colloidal alpha iron. According to the conditions of manufacture the samples occur as (1) large, well-formed dendrites, (2) shorter, more fragile dendrites, (3) serrated rods, (4) needles and (5) cubic particulates. The central stem is a line-up of single cubic crystals. Representative dimensions are given for the various measurable units. A fine laminar structure in the cubic particulates, and some of the side branches and main stems is noted. The same laminar structure is observed in some of the background platelet material from the mother liquor. Stereoscopic studies show that the dendrites are three dimensional with their branches and main stem not in the same plane. X-ray diffraction detects alpha iron plus some form of Fe2O3 in most samples.ZusammenfassungEs werden elektronenmikroskopische Aufnahmen mit hohem Auflösungsvermögen von kolloiden α-Eisenteilchen gezeigt. Entsprechend den Herstellungsbedingungen fallen die Teilchen als gro\e, gut ausgebildete Dendriten, als kürzere schwÄchere Dendriten, als gezackte Stangen, als Nadeln und als kubische Partikeln an. Der zentrale Stamm ist eine lineare Anordnung aus einzelnen kubischen Kristallen. ReprÄsentative Dimensionen sind für die verschiedenen me\baren Einheiten eingezeichnet. Eine fein laminierte Struktur der kubischen Teilchen und von einigen SeitenÄsten und Hauptachsen ist zu erkennen. Dieselbe Laminarstruktur wird teilweise an dem plÄttchenartigen Material, das als Untergrund aus der Mutterflüssigkeit dazwischen liegt, beobachtet. Stereoskopische Aufnahmen zeigen, da\ die Dendriten dreidimensional sind und da\ Seitenzweige und Hauptachsen nicht in der gleichen Ebene liegen. Röntgeninterferenzen lassen aufα-Eisen, sowie eine Form von Fe2O3 in den meisten Proben schlie\en.

Electron Microscopic Observations of Stromatolysis in Human Erythrocytes.

Summary Widely different degrees of stromatolysis were observed electron microscopically in erythrocytes which occurred in preparations of Treponema carateum taken from tissue fluid of skin lesions. A comparison of electron images with light microscopic images of cells under controlled conditions of stromatolysis showed striking similarities. Isolated appearances in the electron micrographs similar to all the stages of disintegration of hemolyzed erythrocytes reported by Furchgott from light microscopy are represented and observed.

The role of electron microscopy in the development of a new science “Crystallurgy”

The strongly developed dendrites and their application in the development of a new science which we have called “Crystallurgy” will now be considered.

An electron microscopical study: Some effects of magnetic field upon single, anisotropic alpha iron crystals and the relation between their fine structure and magnetic properties

In this discussion of the magnetic properties of these same crystals we are dealing only with those forms which we have described previously as “rods”, “needles”, “nodular rods” or “dendrites with relatively short secondary arms”. Except for their small dimensions, these microscopic crystals are somewhat like “whiskers”, in that they appear to be single and are monolithic as far as our observation can detect. Monolithicity cannot be demonstrated in the more complex forms of the dendrites where overlapping of structures confuses observation, but in the less complex forms, namely rods and needles, it is seen that there is no beadlike appearance, as is observed in iron particles made by a process of electro-deposition into mercury (1). They would therefore be expected to act with the magnetic behaviour associated with shape anisotropy, and as elongated, single crystals, rather than as strings of separate crystals. As such they would be expected to yield exceptionally high coercive force when compacted and aligned.