Explanation for the insensitivity to tilts of the electron diffraction patterns of amphibole asbestos fibers

Our plain-English summary of Explanation for the insensitivity to tilts of the electron diffraction patterns of amphibole asbestos fibers, by K. Seshan (Environmental Research, 1977).

The study

• Author: K. Seshan
• Journal: Environmental Research
• Published: 1977;14(1):46-58
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This laboratory study examined how single amphibole asbestos fibers diffract electrons in a transmission electron microscope. It did not study people or disease. Fibers from UICC standard asbestos samples were placed on carbon-coated grids and tilted while their diffraction patterns were recorded. The published figures show an isolated UICC crocidolite fiber. The patterns did not change noticeably for tilts of up to about 20 degrees either way, which confirmed an earlier report by Skikne and colleagues. Patterns from the UICC fibers were too complex to index directly. Naturally occurring amphibole crystals with a less developed fibrous form gave indexable patterns. The author proposed two explanations for the insensitivity to tilting. For small tilts, it comes from the thinness of the crystals: a calculation for crystals about 100 angstroms thick predicted that tilts of up to 12 degrees might be needed to remove a reflection. For larger tilts, it comes from the minerals' pseudohexagonal symmetry. The author concluded that the clinoamphiboles (amosite, crocidolite and tremolite) are difficult to tell apart by lattice measurements from single-fiber diffraction patterns. The author suggested that X-ray microanalysis is possibly applicable.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory electron microscopy and electron diffraction study of mineral fibers, with a proposed crystallographic model
• Who was studied: Fibers from UICC (Union Internationale contre le Cancer) standard asbestos samples on carbon-coated electron microscope grids. They were examined in a Philips 301 and a Siemens 102 electron microscope. The number of fibers examined is not stated.
• Exposure: No human exposure was studied. The materials were UICC amphibole asbestos fibers: tilting is shown for an isolated UICC crocidolite fiber, and the discussion concerns the three clinoamphiboles amosite, crocidolite and tremolite. X-ray photographs of actinolite were also used.
• Main results:
  • Selected area diffraction patterns of single amphibole fibers did not change noticeably for tilts of plus or minus 20 degrees. This confirmed the earlier observations of Skikne et al.
  • Diffraction patterns from the UICC samples could not be indexed straight away because of their complexity. Naturally occurring amphibole minerals with poorly developed fibrous form gave indexable patterns.
  • The c-axis spacing between rows of diffraction spots was calculated to be in the range 5.27 to 5.30 angstroms for the three clinoamphiboles studied.
  • High-resolution imaging showed the widely spaced 9.5-angstrom lattice planes lying along the fiber axis, as the model assumed.
  • Assuming crystal areas about 100 angstroms thick, the thin-crystal model predicted that tilts of up to 12 degrees may be needed to eliminate a given reflection.
  • The author attributed the apparent absence of change with tilts about the fiber axis to the pseudohexagonal symmetry of these crystals.
• The authors' conclusion: The author concluded that the clinoamphiboles are difficult to distinguish by lattice parameter measurements from selected area diffraction patterns, contrary to suggestions by Clarke and Rudd (1974). The author stated that X-ray microanalysis is possibly applicable when only isolated fibers are available.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Asbestos.

Related studies

• The nature of electron diffraction patterns of amphibole asbestos and their use in identification — J.L. Hutchison, E.J. Whittaker (1979)
• Electron diffraction patterns of U.I.C.C. asbestos samples — M.I. Skikne, J.H. Talbot, et al. (1971)
• Scanning electron microscopy and transmitted electron backscatter diffraction examination of asbestos standard reference materials, amphibole particles of differing morphology, and particle phase discrimination from talc ores — B.R. Bandli, M.E. Gunter (2014)
• The utility of electron microscopy in detecting asbestos fibers and particles in BALF in diffuse lung diseases — T. Kido, Y. Morimoto, et al. (2017)
• Analytical Transmission Electron Microscopy of Amphibole Fibers From the Lungs of Quebec Miners — M. Germine, J.H. Puffer (2015)
• Structural information in diffuse diffraction patterns — J.H. Konnert (1974)

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