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Organization and Management of a Radiation Safety Office
Published in Kenneth L. Miller, Handbook of Management of Radiation Protection Programs, 2020
Steven H. King, Rodger W. Granlund
Monitoring and dosimetry of diffraction units should be designed for low-energy X-rays. Only a few ion chambers give a suitable response for the low-energy X-rays, and dosimeters with dimensions small enough for direct beam measurement are rare. TLDs are suitable if proper corrections are made. Personnel monitors must also be chosen carefully and holders made of materials, such as polyvinylchloride, that have a high atomic number relative to tissue and air should be avoided.
Lasers in Medicine: Healing with Light
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
What is light? You may have encountered several answers to this basic question – that light is a stream of particles, or that it is a wave, or, even more puzzling, that light has both particle and wave properties. In the situations discussed in Chapter 2, for example, light travels in straight lines unless reflected or refracted, much as though it consisted of streams of particles shot from a source. On the other hand, when light shines through tiny holes or travels around small obstacles, it no longer follows a straight-line path and can no longer be adequately described using rays. We can see this by placing an opaque screen with a hole in front of a small lamp, and a second screen to capture an image of the hole, as shown in Figure 3.3. If the hole is not too small the image is a bright disk, as we would obtain by tracing rays from the lamp through the hole (Figure 3.3a). However, if the hole is small enough, instead of a single bright disk, we surprisingly get a series of concentric dark and bright circular bands around the central bright spot (Figure 3.3b). Note that the bright bands become dimmer the further they are from the center. The appearance of the bright and dark bands shows that light deviates from a straight path as it passes through the hole. This spreading or bending of light around edges is called diffraction. A similar effect occurs when water waves pass through holes or around obstacles.
The reflexive autoethnographer
Published in Kay Aranda, Critical Qualitative Health Research, 2020
Lisa Mazzei (2014) celebrates the significance and importance of diffraction in the need to trouble the longstanding and habitual practices of conventional qualitative inquiry described above. She argues that the basis of these practices in a general strategy of mechanistic coding and reducing data to themes robs storied life of its entangled complexities, richness and surprises. In response to this state of affairs, and in line with the seminal work of Karen Barad (2007), Mazzei (2014, p. 742) argues for diffraction as a highly productive methodological strategy of ‘reading insights through one another’. This phrase refers to thinking about qualitative data with social, human and other scientific theoretical concepts in multi-layered ways, where these theoretical concepts are ‘plugged into’ data (Jackson & Mazzei, 2012). This allows for a better, richer, more entangled and complex portrayal of life through emergent and unfolding, shifting, unpredictable and unfamiliar, thoughts, meanings and juxtapositions. If you engage with it, diffractive writing will help you productively transgress normative epistemological assumptions and practices through producing knowledge differently and producing different knowledge (Klevan et al., in press).
Steering light in fiber-optic medical devices: a patent review
Published in Expert Review of Medical Devices, 2022
Merle S. Losch, Famke Kardux, Jenny Dankelman, Benno H. W. Hendriks
Refraction is defined as the change in direction of a transmitted light beam after it enters a second medium. Reflection is defined as the change in direction of a light beam at an interface that returns the light beam back to the original medium. The angle of incidence of the light beam on the surface and the material properties of the two media determine the intensity and direction of the refracted and reflected light beam. Another way to steer light is scattering: multiple changes in refractive index force the light beam to randomly change direction in a series of reflection events, resulting in diffuse light scattering. Lastly, a fundamentally different method to steer a light beam is diffraction. Diffraction is defined as the bending of light after encountering a small opening or obstacle. The light beam does not bend in one direction; instead, a diffraction pattern is generated by the interference of different wave fronts. Diffraction is predominant for apertures and obstacles with sizes in the range of the wavelength of the incident light.
Fabrication and transplantation of chitosan-selenium biodegradable nanocomposite conduit on transected sciatic nerve: a novel study in rat model
Published in Neurological Research, 2020
Salar Dolkhani, Alireza Najafpour, Rahim Mohammadi
The structural characterization and size of selenium nanoparticles were studied using Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). In order to study the interaction between nanoparticles and polymer, fourier transform infrared spectrophotometry (FTIR) (Shimadzu, FTIR-8400) analysis was conducted to verify the occurrence of chemical bonds between the drug and the polymer. The samples were scanned in the IR range from 500 to 4000 cm−1 and carbon black was used as a reference. The detector was purged carefully with clean dry helium gas to increase the signal level and reduce moisture (Figure 1). Philips diffractometer was used to obtain X-ray diffraction pattern. X-ray diffraction (XRD) patterns were acquired from 2θ = 10° to 80° using Cu Kα1 radiation. Transmission electron microscope (Philips ES 30 KW0 was used to determine size of nanoparticles. The size distribution of the nanoparticles was detected through Zetasizer Nano ZS (Malvern Instruments Limited)) particle analyzer.
The structural basis for the selectivity of sulfonamido dicarbaboranes toward cancer-associated carbonic anhydrase IX
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Michael Kugler, Josef Holub, Jiří Brynda, Klára Pospíšilová, Suzan El Anwar, Dmytro Bavol, Miroslav Havránek, Vlastimil Král, Milan Fábry, Bohumír Grüner, Pavlína Řezáčová
Complexes of CA II or CA IX-mimic with compounds were prepared by addition of a onefold to twofold molar excess of the compounds (dissolved in 100% DMSO) to a 20 − 25 mg/ml protein solution in 50 mM Tris-H2SO4, pH 7.8. The final concentration of DMSO in crystallisation drops did not exceed 10%. Crystals were prepared by the hanging drop vapour diffusion method at 18 °C using EasyXtal® 15-Well Plates (Qiagen). Drops containing 2 μl of the complex solution were mixed with 1 μl of the precipitant solution and then these mixtures were equilibrated over a reservoir containing 1 ml of the precipitant solution. The precipitation solution consisted of 1.6 M sodium citrate, 50 mM Tris-H2SO4, pH 7.8. Crystals formed within one to three weeks. Prior to data collection, the crystals were soaked for 10 s in the reservoir solution supplemented with 20% (v/v) sucrose and stored in liquid nitrogen. X-ray diffraction data at 100 K were collected on BL14.1 and BL14.2 operated by the Helmholtz-Zentrum Berlin (HZB) at the BESSY II electron storage ring (Berlin-Adlershof, Germany)45. Diffraction data were processed using the XDS suite of programs46,47. Crystal parameters and data collection statistics are summarised in Supporting Information Table S1–S2.