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Scintillation Fiber Optic Dosimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
The numerical aperture (NA) is an important parameter of optical fibers in quantifying their ability to collect light and radiate outgoing light. NA is related to the critical angle in the fiber that defines a cone of angles within which all rays are guided in the fiber by total internal reflection, as shown in Figure 9.1. Mathematically, , where no is the refractive index of the medium in which the fiber's tip is inserted ( = 1 for air) and is the half-angle of the fiber's acceptance cone, as illustrated in Figure 9.1. Practically, the NA is defined as the sine of the angle at which the output optical power falls to 5% of the peak value. When two fibers are coupled, it is important to match their NA to optimize the coupling efficiency. Special couplers are designed to optimize the coupling between the fibers by matching their NAs. Coupling loss and reflection losses at both ends of the fiber can be minimized by antireflection coating of the fiber ends.
Immunocytochemical Detection Systems
Published in Lars-Inge Larsson, Immunocytochemistry: Theory and Practice, 2020
This theoretical physical reasoning has several practical implications for the construction of the microscope. The older generation of fluorescence microscopes made use of transmitted light. To prevent the transmitted light from reaching (and damaging) the eyes of the observer and obscuring the image, dark-field condensers were employed. Such condensers operate at different levels of quality with different objectives. Therefore, one major innovation in the field has been the introduction of epi-illumination systems, in which the objective simultaneously acts both in its original capacity and as a condenser to illuminate the specimen.175,274 In this way, only reflected exciting light and emitted light will re-enter the objective. The reflected exciting light will be removed by the dichroic mirrors and secondary filters of the system. A second major advance has been the introduction of immersion objectives of high numerical apertures also for low-magnification fluorescence work. In this way, the loss of emitted light by reflection (which is considerable with nonimmersion, low-power objectives of long operating distance) is nearly totally avoided. Purchase of a new fluorescence microscope without immersion objectives is not recommended. Such objectives are now available from the major microscopy firms.
Bioengineering Aids to Reproductive Medicine
Published in Sujoy K. Guba, Bioengineering in Reproductive Medicine, 2020
A high numerical aperture with concomitant large acceptance angle has certain advantages. At the proximal end of the fiber bundle, light will be collected from a large area and the net light trapped and transmitted will be high. At the output end the light will diverge out at the same angle as the acceptance angle provided that the field is air. If the field is water as happens in cystoscopy and liquid filled uterine cavity the divergence angle is reduced. With a large divergence angle larger area is illuminated and it is convenient in obtaining a panoramic view. But a high numerical aperture is not an unmixed blessing. As seen from Equation 3.14 a high numerical aperture is obtained by selecting high refractive index core material. With such a material the light loss in the blue region of the spectrum rises. So if at the input end a spectrally balanced white light enters the fiber bundle, at the output, the light will have depleted blue components thus affecting color contrast perception. In practice therefore a comparatively lower numerical aperture than what can be realized is adopted. At the input a spectral dominance of blue is maintained. To increase the area of illumination, divergence angle is raised by having a tapered fiber cone coupling between the flexible light cable and the rigid fiber bundle within the endoscope.
Curcumin-loaded microemulsion: formulation, characterization, and in vitro skin penetration
Published in Drug Development and Industrial Pharmacy, 2023
Irene Carolina Luna-Canales, Norma Laura Delgado-Buenrostro, Yolanda I. Chirino, Guadalupe Nava-Arzaluz, Elizabeth Piñón-Segundo, Graciela Martínez-Cruz, Adriana Ganem-Rondero
In order to determine the penetration pattern of CUR into the skin, Confocal Laser Scanning Microscopy was used. Once the permeation study was completed, the pigskin was recovered, and the excess CUR was removed by rinsing with saline solution. Subsequently, an immunofluorescence treatment was applied, permeabilizing the skin with a 1% TritonTM X-100 solution. The samples were incubated with a mixture of a solution of 10 μg/mL of rhodamine-conjugated phalloidin and a solution 1:1000 of Hoechst in PBS. Next, each skin section was fixed between a slide and a coverslip, placing a drop of PBS:glycerol (1:1) on each sample, keeping them in the dark at 4 °C. The samples were analyzed with a Confocal Laser Scanning Microscope (Leica TCS SP8, Germany), without any type of mechanical sectioning. The CUR was excited at a wavelength of 488 nm using an Argon laser [20]. The samples were analyzed with a numerical aperture of 10×/0.4.
Anti-biofilm activities of coumarin as quorum sensing inhibitor for Porphyromonas gingivalis
Published in Journal of Oral Microbiology, 2022
Zhiyan He, Wei Jiang, Yiting Jiang, Jiachen Dong, Zhongchen Song, Jianrong Xu, Wei Zhou
The structure of P. gingivalis biofilms, grown as described in the above assay of biofilm formation and dispersion in the presence or absence of coumarin, was observed by a confocal laser scanning microscope (CLSM). The biofilms formed on the glass-bottom chamber slides were treated with L-7012 LIVE/DEAD BacLight TM bacterial cells (Molecular Probes Inc., Eugene, OR) containing SYTO 9 dye and propidium iodide according to the manufacturer’s instructions. A confocal laser scanning microscope (Leica TCS SP2, Leica microsystems, Germany) was used to record image stacks in five random locations. Five confocal data sets were recorded at 40 × magnification with a numerical aperture of 1.25. In each experiment, the exciting laser intensity, background level, contrast, and electronic zoom were maintained at the same level.
A new thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes
Published in International Journal of Hyperthermia, 2022
H. T. I. Assi, M. G. Arsenault, W. M. Whelan, J. C. Kumaradas
Thermal dose models are needed for clinical applications like cancer treatment where temperatures vary spatially and temporally during treatment. Ex-vivo liver heating experiments were performed to test the performance of the thermal dose models under such realistic conditions. In this experiment, six thermal lesions were created on the surface of an adult bovine liver sample using laser energy. The sample was originally frozen, and was brought quickly to room temperature before the start of the experiment. The tissue was allowed to cool to room temperature after the creation of each lesion. A multimode optical fiber with a 1 mm core diameter and 0.37 numerical aperture (ThorLabs, Newton, NJ, USA), coupled to a Diomed 60, 810 nm diode laser (Diomed, Cambridge, UK) was placed 13 mm away from the tissue surface. A constant laser power of 1.3 W − 1.6 W for 1 min. to 6 min. exposures was used to produce lesions of varying size and temperature histories. The surface temperature map for each lesion was collected during heating using a thermal camera (FLIR ThermaCAM SC2000, FLIR Systems, Burlington, On, Canada) with a Close-up lens (34 mm horizontal field-of-view and 80 mm focal length) at a rate of one frame per second. The thermal camera continued to collect data two minutes after the laser was turned off since damage keeps accumulating after heating has stopped. Temperatures at the end of this period were too low to accumulate more damage significantly.