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Scanning Angle Interference Microscopy (SAIM)
Published in Qiu-Xing Jiang, New Techniques for Studying Biomembranes, 2020
Cristina Bertocchi, Timothy J. Rudge, Andrea Ravasio
SAIM was described for the first time by Paszek and colleagues22 as an improvement of the theory and methodology of the above described surface-generated structured illumination microscopy techniques (Figure 4.1c). In SAIM, a silicon wafer with a silicon oxide layer of only one defined thickness is used as a spacer, thereby simplifying substrate preparation. The reflection of coherent excitation light interferes with the incoming beam and generates a standing wave pattern, resulting in fluorescence intensity that varies with distance from the surface. The incidence angle of the light is varied, modifying the standing wave pattern, and a series of images at different angles between the center and the maximum incident angle is recorded. By fitting the raw interference images to a mathematical model that describes how excitation intensity varies as a function of height and incidence angle of the excitation laser, it is possible to reconstruct the z-position of fluorescent molecules with 10 nm or better precision.
Practical Implementations And Technology Of Measurement Devices*
Published in Marvin C. Ziskin, Peter A. Lewin, Ultrasonic Exposimetry, 2020
Angular response — The TDS technique can also be used to measure another important hydrophone parameter, namely, the angular sensitivity response or directivity pattern. The directivity pattern can be obtained in the following way. A number of voltage sensitivity measurements are taken as the hydrophone is rotated about an axis parallel to the plane containing the central sensitive spot. This provides response spectra as a function of incidence angle. This information can be subsequently plotted for any frequency over the range of measurements. Figure 4 shows an example of the angular sensitivity response measured in water at 2 MHz for the two hydrophone configurations discussed.
Telescopes for Inner Space: Fiber Optics and Endoscopes
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
Consider the following sequence of events (Figure 2.10) that happens when rays of light hit an interface at glancing angles. At the top of each diagram, light is incident on an interface between glass (the top medium) and air (the bottom medium). A typical value for the index of refraction of glass is 1.5, and that of air is very close to 1.00, so the light travels from a high index of refraction (low speed) to a low index of refraction (high speed) medium. For each of the incident angles, the reflected ray always makes an angle equal to the original ray. However, as the rays of light pass through the interface, the refracted rays are bent into angles greater than those of the incident rays. Eventually, an incident angle is reached for which the refracted ray is bent almost 90°, skimming the surface (Figure 2.10d). What happens to the refracted ray if the incident angle becomes even greater? The refracted ray has been bent as far as it can go without re-entering the original medium! In fact, for angles greater than the angle shown in Figure 2.10d, there is no refracted light. All of the incoming light is reflected, a phenomenon called total internal reflection. Even though we ordinarily think of the interface between air and glass as transparent, for a special range of angles, the light is reflected from the interface as if from a perfect mirror!
Recent approaches to ameliorate selectivity and sensitivity of enzyme based cholesterol biosensors: a review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Anjum Gahlaut, Vinita Hooda, Vikas Dhull, Vikas Hooda
Surface plasmon resonance biosensor is a kind of optical biosensor. Surface plasmon resonance transducers measure changes in refractive index of surface of the sensing element. When plane polarized incident light passes through the prism and strikes the metal at an adequate angle, it induces a resonant charge wave at the metal/dielectric interface that propagates a few microns. The total reflection is measured with a photo detector, as a function of the incident angle. For example, when an antigen binds to an antibody which is immobilized on recognition layer it is found to have increased reflectivity. This increase in reflectivity is due to the presence of antigen on the surface and directly proportional to its concentration [13].
Effect of silica nano-spheres on adhesion of oral bacteria and human fibroblasts
Published in Biomaterial Investigations in Dentistry, 2020
Pawel Kallas, Hua Kang, Håkon Valen, Håvard Jostein Haugen, Martin Andersson, Mats Hulander
X-ray photoelectron spectroscopy (XPS) was performed to confirm the removal of the amine containing 3-(ethoxydimethylsilyl)propylamine used for nanoparticle immobilization and to ensure similar surface chemistries on the smooth and nanostructured parts of the sample. Analyses were performed on areas measuring 400 × 500 µm, probing to a depth of ∼5 nm, using a Versa Probe III Scanning XPS Microprobe (Physical Electronics Physical Electronics, Inc., Chanhassen, MN) equipped with a monochromatic Al Kα (1486.6 eV) X-ray source. All measurements were performed at an incident angle of 45°. The measurements were performed on the bi-functional surfaces.
Mathematical and computational modeling for the determination of optical parameters of breast cancer cell
Published in Electromagnetic Biology and Medicine, 2021
Shadeeb Hossain, Shamera Hossain
The transmittance and reflectance coefficient is pursuant to critical angle of tissue sample. This incident angle is the optimum threshold beyond which the electromagnetic wave undergoes total internal reflection when it strikes the tissue surface. Simultaneously, this optical parameter also describes the evanescent wave propagation and shifting dynamics in wave velocity through tissue. Therefore, critical angle is a disinterested non-invasive parameter, for malignant tissue diagnosis.