The Microscope - Volume 64, First Quarter 2016
IN THIS ISSUE:
On the cover
Photomicrograph showing modacrylic fibers from a costume wig, mounted in xylene; plane polarized light. See Capillary Microspectrophotometry of Some Selected Dyed Fibers and Hairs on page 3.
Editorial | The Spirit of Cornell’s Chemistry Society Lives On
Gary J. Laughlin
The Microscope 64 (1), p ii
Excerpt: Occasionally, while sifting through the collections here at Microscope Publications, I will happen upon an unusual remnant from Walter C. McCrone’s past (that I can talk about), and such is the case of the Al’Djebar songbook. Al’Djebar was a convivial gathering of Cornell chemistry students that was active at the university from 1921 to 1948. I hadn’t seen the songbook since Dr. McCrone hired me in 1987, while I was studying criminalistics and chemistry at the University of Illinois at Chicago. I worked with him at McCrone Research Institute for 15 years until his death in 2002. … Together with the songbook, I have also discovered Lauby’s written recollections and a photograph taken in July 1941, which shows 19 gentlemen in an Al’Djebar meeting, including McCrone…
Capillary Microspectrophotometry of Some Selected Dyed Fibers and Hairs
Katelyn A. Hargrave, Skip Palenik, Ethan Groves, Jason C. Beckert, and Christopher S. Palenik
The Microscope 64 (1), pp 3 – 11
Abstract: Colorants from dyes observed on fibers and hairs in trace evidence examinations are commonly compared via polarized light microscopy, comparison microscopy, microspectrophotometry, and in some cases, chromatography. Some of the most difficult samples to evaluate and compare by these methods include lightly dyed fibers (which result in a “noisy” and nearly featureless spectrum due to a low signal-to-noise ratio), heavily dyed fibers (resulting in the nearly complete absorption of the incident illumination), and heterogeneously dyed fibers, e.g., vegetable fibers, which provide a range of spectral intensities that complicate interpretation. Here the authors present a method for the extraction and subsequent analysis of dyes directly from fibers. This approach relies upon the use of a borosilicate glass flat microcapillary cell (i.e., a low volume, fixed-path length cell) to hold the extract that can then be analyzed by a microspectrophotometer (MSP). This capillary microspectrophotometry (cMSP) method provides a means to obtain reproducible spectra of the dyes from many problematic fibers.
Determination of the Size Distribution of Amphibole Asbestos and Amphibole Non-Asbestos Mineral Particles
D.R. Van Orden, R.J. Lee, C.M. Hefferan, S. Schlaegle, and M. Sanchez
The Microscope 64 (1), pp 13 – 25
Abstract: Over the last few years, there have been a number of investigations into the presence of amphibole minerals in soil or bedrock throughout the U.S., resulting in remediation of school grounds or highway right-of-ways, or delayed construction of needed dams. A review of available data suggests that the identified amphibole minerals were called “asbestos” simply based on being elongated particles and may not have been asbestos fibers. To clarify the characteristics of amphibole minerals, a study was conducted to characterize the size distributions of amphibole asbestos fibers and non-asbestos amphibole particles to determine differences and similarities between the populations. Ten mineral samples that could be visually characterized as asbestos or non-asbestos were obtained (five of each). Each sample was ground, suspended in water and deposited onto a 0.2 µm pore-size polyester filter. The filters were imaged in a field emission scanning electron microscope at magnifications up to 18,000x. The images were processed to obtain the length and width of particles that were at least 2 µm long and less than 3 µm wide (no minimum aspect ratio was applied). The data show there are clear differences in the dimensions of populations of asbestos and non-asbestos amphiboles, with asbestos being thinner and having a higher aspect ratio than non-asbestos. In addition, there is a set of particles in the asbestos samples that were not observed in the non-asbestos samples: fibers longer than 10 µm, thinner than 0.5 µm, and that have aspect ratios in excess of 30:1.
Critical Focus | Cloudy with a Chance of Microbes
Brian J. Ford
The Microscope 64 (1), pp 27 – 39
Excerpt: Everyone is talking about the weather, and climate change is high on the global agenda. They are not the same: Climate is what you expect; weather is what you get. We believe that our weather derives from physical forces, but there is a far more remarkable mechanism at work. Much of our climate, surprising as it seems, is controlled by the microbe world. It is microbes that created the oxygen we breathe, the carbon sinks of the world are under microbe control, and clouds form because of microbial action. Yet the microscopic realm is rarely brought into the discussion. Humans have upset this balance of nature, and we have tipped the atmosphere into a dangerous state.
Tricks of the Trade | How to Make a Residue-Free Particle Disperser
The Microscope 64 (1), pp 41 – 44
Excerpt: One of the basic tools that a particle analyst needs during microscopical research is a particle disperser, which is used to gently crush and then disperse particles between a microscope slide and coverslip. The standard tool employed for this purpose in many laboratories is the soft eraser on typical graphite (“lead”) pencils or a pencil with two erasers. These pencil erasers are soft enough to gently dissipate the pressure applied to the preparation and stiff enough to make brittle particles break.
Afterimage | Acetylsalicylic Acid
The Microscope 64 (1), p 48
Photomicrograph showing the active ingredient in an aspirin tablet (acetylsalicylic acid) recrystallized from the melt; crossed polars and Red I compensator. Image width is 1.4 mm.
Copyright © 2016 Microscope Publications, Division of McCrone Research Institute. All rights reserved.