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SUMMARY Easy preparation of thin crystalline specimen supports for high resolution electron microscopy has been achieved by thermic exfoliation of vermiculite. The thinnest layers obtained appear to be 1·8 nm thick and show the expected hexagonal array with a 0·46 nm lattice spacing. This periodic background could be suppressed either by optical filtering or by putting a zero crossing of the respective transfer function of the electron microscope objective over the diffraction spots of the crystal.

The alteration of organic materials during burial is similar to thermally induced carbonization. High resolution electron microscopy shows that samples of either natural or heat-treated kerogens are formed by stacks of two aromatic layers of 5–8 A in diameter. During catagenesis and heat-treatment, these stacks orientate themselves parallel to each other and form clusters of increasing diameter.

A critical survey of the published data of the focal properties of magnetic electron lenses has revealed several inconsistencies between the findings of various authors. Some of these can be ascribed to errors in computation, but others stem from inherent limitations imposed by the conventional presentation of results in the form of `universal' curves or from the use of relative rather than fixed units, such as centimetres. The results of more accurate computations, especially of spherical aberration, are presented in a new form which is particularly suited to the determination of lenses of optimum performance. The results are applied to the question of determining the best possible objective lens for high resolution electron microscopy.

The development of the electron microscope microanalyser (EMMA 4) is briefly reviewed. It is pointed out that while in principle any ultra-thin specimen can be examined, chemical treatment will remove certain substances. In this connection, the use of EMMA 4 has been helped by developments in cryo-ultramicrotomy. While at present elements lighter than sodium cannot be detected there is nothing in principle to prevent the range from being extended to elements of lower atomic number.

Heat treatment of MgF2, Nb2O5 mixtures has been used to form complex oxides possessing „block structures”. By means of high resolution electron microscopy it is possible to observe the component blocks and to identify defects at the unit cell level. Interaction of planar defects within such crystals gives rise to anomalous structures, including hitherto unreported extended linear defects in the form of rectangular tunnels. Their cross-section, 2.8 × 5.6 A2, is within the resolving power of the electron microscope and at the appro-priate defocus they appear as white streaks in the lattice image. [Russian Text Ignored].

High resolution electron microscopy has been used to examine thin films of natural rubber and other polymers. Dispersions of various materials (in particular neoprene and chlorinated natural rubber) in natural rubber have been studied. Structures which are believed to be the individual curled-up molecules of the dispersed polymer have been photographed. Stretched rubber films have also been examined and some information about the mode of deformation obtained.

The results obtained by the application of five different methods to stain with silver methenamine thin sections of tissue for electron microscopy are described and evaluated in this article. Three of these methods lend themselves to wide applications in that they enhance vividly the argentophilic structures without inducing excessive graininess of the staining. The latter appears to be due mainly to prolonged and unnecessary exposure of the sections to the staining solution. The graininess observed in specimens prepared under the most favorable conditions, however, is still too coarse to allow the application of this technique for high resolution electron microscopy.

The imaging improvement method recently proposed by Stroke and Halioua for conventional electron microscopy has now been successfully demonstrated with an electron micrograph of a T2 bacteriophage virus originally photographed with heretofore unsurmountable “blurring” characteristic of defocusing phase contrast.

Images of the (001) planes of muscovite were observed by electron microscopy after embedment of clay-size flakes in epoxy resin and sectioning by ultramicrotome. Dislocation or growth planes were indicated. Incomplete exchange of potassium for barium produced zones with 20-angstrom periodicity, suggesting regular interstratification.

Die prinzipielle Konstruktion eines neuen Mikrotoms zur Herstellung ultradunner Schnitte wird beschrieben. Mit diesem Mikrotom sind Schnitte hergestellt worden, die dunner als 100 A waren.

The phase contrast transfer function (CTF) for imaging of weak phase objects in high resolution electron microscopy is well known. It is an oscillating function, generating transfer intervalls with positive and negative contrast. Due to the influence of chromatic aberration and partial coherence its amplitude decreases at higher spatial frequencies. Several attempts have been made to improve the CTF by a posteriori optical filtering, e.g. zonal filtering or the use of Tsujiuchi-type phase filters. The method of holographic deconvolution, as proposed by Stroke and Halioua, employs phase and amplitude filters in such a way that the CTF approaches nearly a constant value.

ALTHOUGH electron microscope contrast may be increased by the use of objective apertures, accurate focusing in thin-section work is still difficult and, in order to obtain an in-focus picture of a particular field, it is very helpful to find a small dense particle, or a hole in the membrane, on which to focus. An obvious solution to this problem is to distribute small dense particles on the specimen.

In preparations of sap removed from sugar beet infected with beet yellows virus, filaments have been concentrated in sufficient numbers to be studied in the electron microscope. Using the negative staining technique, the virus appears as a filamentous structure 10 m μ in diameter and one to several microns long. The filaments have a regular periodicity and a central hollow core. Small hollow particles 10 m μ in diameter, observed in infected sap, may be short pieces of filament. The methods of preparation are discussed and dimensions compared with tobacco mosaic virus.