The Microscope - Volume 68, Third/Fourth Quarters 2020
IN THIS ISSUE
On the cover:
A highly altered and degraded Dimetrodon bone; epi-illumination combined with ≈30% transmitted light. See Optical Method for Characterizing Opaque Regions of a Fossil Thin Section, page 132. (Photomicrograph courtesy of James Solliday)
Editorial | Doubling Down After a Rough Patch
Gary J. Laughlin
The Microscope 68 (3-4), p ii, 2020
Excerpt: We are happy to present this latest edition of The Microscope as a full 96-page double issue, Volume 68, Third/Fourth Quarter 2020. It was an absolute necessity to combine two issues, as all of our operations — educational, research, symposia, and publications — were either canceled, postponed, or suspended for the first half of 2021 and the prior year due to the Covid-19 pandemic. To say this has been a rough patch for all would be an understatement, though I am glad we are here to write about it, while looking ahead to a favorable future.
Comprehensive Suite of d-θ Look-Up Tables for Indexing Zone-Axis SAED Patterns of Amphibole Asbestos and Related Minerals
The Microscope 68 (3-4), pp 99 – 110, 2020
Abstract: The analysis of asbestos minerals below optical resolution is conducted by the analytical transmission electron microscopy (TEM). The Asbestos Hazard Emergency Response Act (AHERA) protocol mandates the measurement of three properties: the morphology by the TEM imaging, the elemental composition by the energy-dispersive X-ray spectroscopy (EDS), and the crystal structure by the zone-axis selected area electron diffraction (SAED). After the acquisition of a zone-axis SAED pattern with EDS-derived mineral identity, the practical and effective methodology of its indexing and interpretation is the comparison of the measured (observed) values of the d-spacings of two intersecting direct lattice planes and their interplanal angle against the reference values in pre-calculated d-spacing and interplanal angle look-up tables (d-θ table) based on the mineral’s unit cell parameters and symmetry. This paper presents a suite of hitherto most comprehensive d-θ look-up tables (more than 800 pages and 36,000 zone axes) for five regulated amphiboles (anthophyllite, grunerite, riebeckite, tremolite, and actinolite), three non-regulated ones (winchite, richterite, and cummingtonite), and talc, which could be confused with the regulated anthophyllite to facilitate the analysis of zone-axis SAED patterns. The procedure of using the d-θ look-up table is illustrated by two examples. Issues relevant to applications of d-θ table are also discussed.
Download/view d-θ Look-Up Tables (PDF):
Actinolite | Anthophyllite | Cummingtonite | Grunerite | Richterite | Riebeckite | Talc | Tremolite | Winchite
Microscopy in the Investigation of Asbestos-Containing Friction Products
James R. Millette, Steven Compton, and Christopher DePasquale
The Microscope 68 (3-4), p 111 – 131, 2020
Abstract: Bulk analyses of approximately 100 asbestos-containing friction products showed levels of chrysotile ranging generally from 15% to 60% by volume. Small amounts of amphibole asbestos (primarily tremolite) were found in over 95% of the brake and clutch products tested. The amphibole asbestos was present in the range of 0.0001 to 0.4% by weight. Although the levels of amphibole asbestos were less than 1% by weight, the concentration of amphibole fibers was in the millions fibers per gram of friction material in many cases. The results of 11 studies of asbestos fiber release from brake materials, conducted by MVA Scientific Consultants (MVA), involved various activities such as sanding, filing, grinding, rivet removal, drilling, sweeping, compressed-air blowing, brake removal, and handling of contaminated clothing are presented. Following acid/base digestion, amphibole asbestos fibers were found in air samples in two of the studies. An analysis of brake wear dust found chrysotile asbestos fibers but no forsterite.
Optical Method for Characterizing Opaque
Regions of a Fossil Thin Section
The Microscope 68 (3-4), pp 132 – 138, 2020
Abstract: Transmitted light microscopy, with brightfield, polarized and crossed-polarized methods of illumination, are often employed in the histological and morphological interpretation of fossil thin sections. These methods are quite sufficient for the carbonate-based regions of the section; however, iron-based areas are often completely opaque and block all transmitted light. In order to study and characterize this opaque region it is necessary to reverse the angle of illumination to expose the top surface of the obscured areas. This technique has rarely been applied to the analysis of fossil thin sections and thus justifies this study in order to determine if the method can be of value. Epi-illumination, which creates brightfield and darkfield epi-illumination (Figures 1 – 2), was found to characterize areas of the section that are obscured to standard light microscopy. In most cases, opaque areas respond with high reflectivity providing clues to its density and composition. Standard thin-section methods are sufficient as long as the exposed surface is polished and preferably no coverslip is applied. The specimen in this study is a thin section of a fossil, 50 µm thick, from the scapula of a Dimetrodon sp. from the Lower Permian period (Figures 3 – 9).
Critical Focus | Forgotten Women Who Lit the Way
Brian J. Ford
The Microscope 68 (3-4), p 139 – 150, 2020
Excerpt: From coronaviruses and genetics to microbiology and botany, the contributions to science by female microscopists have been significant, though were often met with bias and apathy. (Pictured: Barbara McClintock, one of America’s greatest cytogeneticists, at Cornell University in 1931)
Measuring Volume and Surface Area
John C. Russ
The Microscope 68 (3-4), pp 151 – 155, 2020
Abstract: High quality computer-gene rated visualizations of 3-D datasets obtained with a variety of microscopies are used in many different fields of application. It seems natural to attempt to perform measurements of the volume within or under a surface, and the area of that surface, as these values can be related to various properties of the subjects. There are concerns, however, with the methods that may be applied to perform the measurements, and it is instructive to examine the consequences of the procedures applied to the raw image data to generate the surface renderings and/or to estimate the 3-D measurements. The effects of these procedures on volumes are relatively modest, but surface areas are highly dependent on the resolution of the original data and the processing and measurement operations, and the results are generally unreliable.
New Microcrystal Tests for Controlled Drugs, Diverted Pharmaceuticals, and Bath Salts (Synthetic Cathinones): MDPV and 4-MEC
Sebastian B. Sparenga, Gary J. Laughlin, Meggan B. King, and Dean Golemis
The Microscope 68 (3-4), pp 156 – 171, 2020
Excerpt: The Microscope is publishing selected monographs from McCrone Research Institute’s recently completed research, New Microcrystal Tests for Controlled Drugs, Diverted Pharmaceuticals, and Bath Salts (Synthetic Cathinones), which contains newly developed microcrystal tests and reagents with 9 additional drugs: alprazolam, butylone, mephedrone, methylone, MDPV, 4-MEC, alpha-PVP, tramadol, and zolpidem. This issue includes the monographs for the following drugs/reagents:
• MDPV/palladium chloride with hydrochloric acid and phosphoric acid
• MDPV/gold bromide with phosphoric acid and
• 4-MEC/palladium chloride with hydrochloric acid and phosphoric acid
• 4-MEC/gold chloride with sulfuric acid
Microscope Past: 35 Years Ago | Fusion Methods Identification of Inorganic Explosives
John H. Kilbourn and Walter C. McCrone
The Microscope 68 (3-4), pp 172 – 179, 2020
Originally published in The Microscope, Vol. 33, Second Quarter, pp 73 – 90, 1985.
Abstract: The 10 alkali chlorates, perchlorates and nitrates, all inorganic explosives, melt at or below 610° C. All can be melted over an alcohol lamp and all crystallize in a characteristic fashion upon cooling. Melting points accurate to better than ±10° C can be estimated for 5 of the 10 by timing carefully controlled heating over an alcohol lamp. Characteristic patterns of each of the 10 compounds as crystallized from melts can be recognized by differences in shape, shrinkage cracks, birefringence, extinction angles and interference figures. A “mixed fusion” with water yields additional information by yielding well-formed individual crystals.
Letters to the Editor | Leeuwenhoek Microscopes and “Nonscience”
The Microscope 68 (3-4), p 180 – 187, 2020
The Microscope: Author and Subject Indexes, Volume 68, 2020
The Microscope 68 (3-4), p 188 – 191, 2020
Afterimage | Victorian Diatom Art
The Microscope 68 (3-4), p 192, 2020
From a vintage slide collection of the State Microscopical Society of Illinois (SMSI); plane polarized light. (Photomicrograph by Meggan King and Sebastian Sparenga/McCrone Research Institute)
Subscribe to The Microscope
Copyright © 2020 Microscope Publications, Division of McCrone Research Institute. All rights reserved.