Low-dose imaging of freshwater rotifers in their original state using advanced ESEM

We have assembled an image processing system for use with our high resolution STEM for the particular purpose of working with low dose images of biological specimens. The system is quite flexible, however, and can be used for a wide variety of images.The original images are stored on magnetic tape at the microscope using the digitized signals from the detectors. For low dose imaging, these are “first scan” exposures using an automatic montage system. One Nova minicomputer and one tape drive are dedicated to this task.The principal component of the image analysis system is a Lexidata 3400 frame store memory. This memory is arranged in a 640 x 512 x 16 bit configuration. Images are displayed simultaneously on two high resolution monitors, one color and one black and white. Interaction with the memory is obtained using a Nova 4 (32K) computer and a trackball and switch unit provided by Lexidata.The language used is BASIC and uses a variety of assembly language Calls, some provided by Lexidata, but the majority written by students (D. Kopf and N. Townes).

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Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126731 ◽

1987 ◽

Vol 45 ◽

pp. 388-389

Author(s):

P. Pradère ◽

J.F. Revol ◽

R. St. John Manley

Keyword(s):

Low Dose ◽

Polymer Concentration ◽

Processing System ◽

Limiting Factor ◽

Dilute Solution ◽

New Techniques ◽

Dose Unit ◽

Lattice Images ◽

Dose Imaging ◽

Imaging Conditions

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.

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Quantitative nano-characterization of heterogeneous catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138361 ◽

1995 ◽

Vol 53 ◽

pp. 398-399

Author(s):

P.A. Crozier ◽

M. Pan

Keyword(s):

Heterogeneous Catalysts ◽

Low Dose ◽

Imaging Techniques ◽

Structural Features ◽

Catalyst Characterization ◽

New Developments ◽

Double Phase ◽

Phase Systems ◽

Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

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