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Experimental Methods in Cardiovascular Mechanics
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
Polarized light microscopy is a contrast-enhancing technique that can be useful for analyzing birefringent (or optically anisotropic) materials. Collagen has a molecular structure that is anisotropic, making it linearly birefringent. It can be stained with Picrosirius red dye to enhance its birefringence and visibility under polarized light. The appearance of type I collagen goes from red to yellow as the fiber diameter decreases, and this effect is associated with a decreased level of birefringence (Whittaker et al. 1994). This optical technique has been used for decades to assess the structure of collagenous tissues and has been combined with uniaxial mechanical testing of tissues such porcine heart valves (Hilbert et al. 1996). However, it is limited in that it provides only qualitative information of the spatial distribution and anisotropy of collagen.
Introduction to Biological Light Microscopy
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
Jay L. Nadeau, Michael W. Davidson
Polarized light microscopy is designed for specimens that are visible due to their optically anisotropic character, such as mineral or protein crystals. The microscope is similar to a brightfield microscope, but is equipped with both a polarizer positioned in the light path somewhere before the specimen, and an analyzer (a second polarizer), placed in the optical pathway between the objective rear aperture and the observation tube. Image contrast arises from the interaction of plane-polarized light with a birefringent specimen to produce two individual wave components that are polarized in mutually perpendicular planes (Figure 7.11). If the polarizers are removed, the microscope becomes an ordinary brightfield instrument. Polarizing microscopes also usually come with specially designed objectives that are strain-free and a rotatable stage. They are often low-magnification binocular scopes that can be used for identification and isolation of crystals (see Chapter 6).
Characterization of HTS Powders and Components
Published in A. G. Mamalis, D. E. Manolakos, A. Szalay, G. Pantazopoulos, Processing of High-Temperature Superconductors at High Strain Rates, 2019
A. G. Mamalis, D. E. Manolakos, A. Szalay, G. Pantazopoulos
Various types of microscopical illumination can be used for HTS material characterization. The most prominent imaging technique is that provided by using polarized light microscopy. In multiphase HTS ceramic systems the various crystallographic phases are characterized by differential contrast under polarized light illumination. The results of the morphological mapping can be treated by using image analysis techniques for quantitative evaluation of the microstructure, e.g., phase and porosity percentages, grain size, etc.).
Detecting a spreading non-indigenous species using multiple methodologies
Published in Lake and Reservoir Management, 2020
Mattias L. Johansson, Sharon Y. Lavigne, Charles W. Ramcharan, Daniel D. Heath, Hugh J. MacIsaac
The first method of analysis was cross-polarized light microscopy (CPLM). Birefringent properties of veligers’ shells (i.e., they have 2 different refractive indices due to their optical properties) cause them to stand out with a distinctive cross pattern against an otherwise dark background under cross-polarized light, allowing them to be efficiently enumerated (Johnson 1995). Prior to the advent of cross-polarized light microscopy, veligers were identified with transmitted light microscopy, which is more prone to false negatives (Marsden 1992). CPLM is widely used for veliger detection in monitoring and surveillance programs (see Hosler 2011), but like transmitted light microscopy it is labor-intensive and time-consuming.