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The Microscope and Examination of the Specimen
Published in Donald L. Price, Procedure Manual for the Diagnosis of Intestinal Parasites, 2017
In the past, critical illumination was used which results in focusing the light at the specimen. Critical illumination is discussed in older texts but is rarely used with modern microscopes. Modern microscopes are designed so that Kohler illumination can be used most effectively. In this system, light is focused at the aperture diaphragm of the condenser for even intensity at the specimen plane.
Effect of titanium dioxide nanoparticles on DNA methylation in multiple human cell lines
Published in Nanotoxicology, 2020
Marta Pogribna, Nathan A. Koonce, Ammu Mathew, Beverly Word, Anil K. Patri, Beverly Lyn-Cook, George Hammons
Dark-field optical microscopy (DFM) and hyperspectral imaging (HSI) was used to study the interaction of TiO2 nanoparticles in cells at room temperature (25 °C). Darkfield microscopy images and hyperspectral measurements were acquired using an enhanced darkfield transmission optical microscope Olympus BX-41 equipped with Cytoviva™ high resolution dark-field condenser (oil immersion), motorized XY stage controller, multiple objective lenses (10× air, 40× air, 100× oil immersion) and hyperspectral imaging spectrometer (Headwall Photonics, Cytoviva Inc., Auburn, AL). The condenser used for this study has both Koehler and critical illumination features and focuses a highly collimated light at oblique angles on the sample. UPLFLN 100XOI2 oil immersion objective (Olympus) with NA of 1.3–0.6 and working distance of 0.2 mm was used for magnification. A L1090 – Halogen Lamp (400–1,000 nm) with Aluminum Reflector (International Light Technologies Inc., USA) was used for illumination of the sample. Optical images were collected using Dagexcel-M Color Camera – Cooled (CCD, 2048 × 2048) high resolution camera. Spectra were measured using the Specim V10E spectrometer (400–1,000 nm) divided into 462 bands, which gives a spectral resolution of ±1.5 nm. To tackle with the lower scattering cross section of ultra-small nanoparticles, measurements were performed at full power illumination of source (150 W) and enhanced camera gain. For fluorescence imaging, a mercury lamp light source (EXFO X-CITE) is used. Light after passing through specific excitation (bandpass) filter falls on the sample. A UV blocking emission filter was used. The emitted light was passed through a triple pass filter and fluorescence (if any) emitted by the particle was imaged.