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Morphology and Properties of Hair
Published in Dale H. Johnson, Hair and Hair Care, 2018
Medulla is present in either continuous or discontinuous form along the axis of coarser α-keratin fibers. Its role essentially is that of empty space, increasing the thermal insulation of the fiber with economy of weight and little loss in bending characteristics. The latter characteristic is of obvious importance for quills, but in the case of human hair is of minor importance. The presence of medulla has an effect on the optical appearance particularly in low-pigmented fibers such as wool. The medulla causes an increase in the scatter of light especially at the blue end of the optical spectrum, making the fibers with a natural yellowish color to appear white. The role of the medulla in physical properties such as mechanical properties is no more than that of empty space. Further discussion of the medulla will be omitted.
Optics of the Skin
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
The goals of this chapter are to 1. present a useful, approximate model of skin optics; 2. elucidate different mechanisms of skin photoprotective response for different parts of the optical spectrum; 3. present data on skin optical properties; 4. discuss ways of altering skin optics that are useful in phototherapy; and 5. present the basis for laser therapy that relies on heterogeneous optical absorption.
Check the Cancer Before It Checks You Out
Published in Prakash Srinivasan Timiri Shanmugam, Understanding Cancer Therapies, 2018
The interaction of light with tissues may highlight changes in tissue structure and metabolism. Optical spectroscopy systems to detect changes relying on the fact that the optical spectrum derived from a tissue will contain information about the histological and biochemical characteristics of that tissue. Such optical adjuncts may assist in the identification of mucosal lesions, including premalignant lesions and oral squamous cell carcinomas; may assist in biopsy site selection and enhance visibility of the surface texture and margins of lesions; and may also assist in the identification of cellular and molecular abnormalities not visible to the naked eye on routine examination. There are a number of optical systems that can yield similar types of information approaching the detail of histopathology, and theoretically at least, in a more quantifiable and objective fashion, in real-time, noninvasively, and in situ (Scully et al. 2008).
Binocular, Accommodative and Oculomotor Alterations In Multiple Sclerosis: A Review
Published in Seminars in Ophthalmology, 2020
Amparo Gil-Casas, David P Piñero, Ainhoa Molina-Martin
Evoked nystagmus has been shown to be present in 45% of patients with MS.84 This type of nystagmus may appear in conjunction with paralysis of the face, imbalance85 and pupillary light-near dissociation.86 Likewise, MS is the second cause of horizontal gaze-evoked nystagmus (hGEN) behind neuromyelitis optical spectrum disorder (NMOSD).87 It is present in between 10-15% of patients with MS.12 Another common type of nystagmus in MS is the acquired convergence-evoked nystagmus (CEN) (40% of patients), which is more frequent in its vertical mode (82%).88 This type of nystagmus can occur as a first symptom89 or in a relapse.90 In this type of nystagmus, lesions occur in cortical eye fields and their descending connections.91
Localization strategies for robotic endoscopic capsules: a review
Published in Expert Review of Medical Devices, 2019
Federico Bianchi, Antonino Masaracchia, Erfan Shojaei Barjuei, Arianna Menciassi, Alberto Arezzo, Anastasios Koulaouzidis, Danail Stoyanov, Paolo Dario, Gastone Ciuti
Visible waves are in the range of the electromagnetic spectrum containing wavelengths from about 390 up to 790 nm. As stated before, since wavelength and resolution are inversely proportional, that is, higher is the wavelength worst is the resolution, localization methods which exploit optical spectrum, could reach better performances than RF-based methodologies. However, unlike the RF-based localization methods, due to their poor penetration through the human tissues, these wavelengths are used for the aim of capsule localization through computer vision techniques. As illustrated in Figure 2(d) by Pahlavan et al. in [71], generally a WCE is equipped with: (i) light emitting diodes, which act as illumination source; and (ii) a miniaturized camera for capturing endoscopic images during its travel along the GI tract. Unlike the previously mentioned localization methodologies, in which the capsule pose was identified with respect to an external reference frame (i.e. external localization), for example, antennas and magnetic sources, images can be used to localize the capsule (and also lesions and pathologies) with respect to the surrounding deformable anatomical environment and targets (i.e. internal localization), for example, landmarks and luminal 3D geometry.
Laser ablation of the biliary tree: in vivo proof of concept as potential treatment of unresectable cholangiocarcinoma
Published in International Journal of Hyperthermia, 2018
Paola Saccomandi, Giuseppe Quero, Riccardo Gassino, Alfonso Lapergola, Ludovica Guerriero, Michele Diana, Alberto Vallan, Guido Perrone, Emiliano Schena, Guido Costamagna, Jaques Marescaux, Francesco M. Di Matteo
Tissue temperature variation measurement is obtained by analysing the optical FBG response. When fed by a polychromatic light source, the grating acts as an optical filter; the reflected narrow spectrum is centred on a value known as the Bragg wavelength (λB) while all other wavelengths are transmitted. When FBG experiences a change in temperature, λB shifts linearly by about 10 pm/°C [25,32]. An optical spectrum interrogator system (Micron Optics Hyperion Platform, Sensing Instrument si155, sampling rate: 10 Hz) was used to interrogate and detect any change in wavelength. The measured temperature data were provided in real time during the experiments with the support of a dedicated software (MOI Enlight, Atlanta, GA).