Microscopical Technique

The structures of E. coli ribosomes have been extensively probed by electron microscopy of negatively stained and frozen hydrated preparations. Coupled with quantitative image analysis and three dimensional reconstruction, such approaches are worthwhile in defining size, shape, and quaternary organisation. The important question of how the nucleic acid and protein components are arranged with respect to each other remains difficult to answer, however. A microscopical technique that has been proposed to answer this query is electron spectroscopic imaging (ESI), in which scattered electrons with energy losses characteristic of inner shell ionisations are used to form specific elemental maps. Here, we report the use of image sorting and averaging techniques to determine the extent to which a phosphorus map of isolated ribosomal subunits can define the ribosomal RNA (rRNA) distribution within them.

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McClung's Handbook of Microscopical Technique

Journal of Clinical Pathology ◽

10.1136/jcp.4.4.497-a ◽

1951 ◽

Vol 4 (4) ◽

pp. 497-497

Author(s):

R. J. V. Pulvertaft

Keyword(s):

Microscopical Technique

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Characterisation of the Fracture Path in ‘Flexible’ Refractories

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.70.30 ◽

2010 ◽

Vol 70 ◽

pp. 30-36 ◽

Cited By ~ 11

Author(s):

Harald Harmuth

Keyword(s):

Characteristic Length ◽

Transgranular Fracture ◽

Matrix Interface ◽

Fracture Path ◽

Figures Of Merit ◽

Microscopical Technique ◽

The Matrix ◽

Specific Fracture ◽

Loss Of Strength ◽

Microscopic Investigations

The denomination ‘flexible’ is chosen in the professional jargon of refractories technology for materials able to bear relatively high strains without or with acceptable loss of strength. In many cases this term is equivalent to relatively low brittleness. Characterisation of brittleness based on fracture mechanical investigations may use figures of merit like brittleness numbers, a so called characteristic length or the R’’’’ parameter according to Hasselman. In many cases these figures show that brittleness reduction of refractories is achieved by decrease of strength with at the same time more or less unaffected specific fracture energy. Microscopic investigations of fracture paths aim to exhibit which peculiarities of crack microstructure enable this change of mechanical properties. A microscopical technique developed for this purpose separately evaluates the relative crack lengths along the grain/matrix interface, within the matrix and within the grain. Results obtained for several types of refractories show brittleness decrease is associated by an increase of the relative crack length along the grain/matrix interface and a decrease of transgranular fracture. Prefabricated microcracks and a relatively low grain/matrix bond strength may support this type of crack propagation.

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