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Calorimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Larry A. DeWerd, Blake R. Smith
The refractive index of a material is related to its temperature. An interferometer can therefore be used to measure the dose to a sample of water by measuring the phase shifts, which occur as the water is heated from the incident radiation. There are several empirical and theoretical mathematical models, which exist that predict water's refractive index dependence on temperature which vary in complexity. One such model was proposed by Abbate [12], who measured the change in refractive index and inferred the following relation:
Scanning Angle Interference Microscopy (SAIM)
Published in Qiu-Xing Jiang, New Techniques for Studying Biomembranes, 2020
Cristina Bertocchi, Timothy J. Rudge, Andrea Ravasio
for light with wavelength and incident angle on the sample , which has refractive index .
Optics of the Skin
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
When the scattering object becomes very large in relation to wavelength, Mie’s theory reduces to familiar optical principles such as the reflection and refraction of light by mirrors, windows, lenses, and other objects, which are governed by the refractive index of the material. Refractive index is defined as the ratio of the speed of light in a vacuum compared to that in the material, and is usually designated as n.
Alternatives to titanium dioxide in tablet coating
Published in Pharmaceutical Development and Technology, 2021
Juliana Radtke, Raphael Wiedey, Peter Kleinebudde
The particle size distribution of the pigments was determined by laser diffraction (Mastersizer 3000, Malvern Instruments, Malvern, UK). For this purpose, all samples were dispersed in water and measured three times using the wet-dispersion unit. The concentration of sample in water was selected in such a way that an optimal laser obscuration of 2 − 6% was guaranteed. Any agglomerates of particles were deagglomerated by ultrasound prior to each measurement. Using the corresponding software, the particle size distribution was determined from the data based on the Mie theory and given as volume distributions. The refractive index was adjusted depending on the material. For ZnO a refractive index of 2.0034 and for TiO2 of 2.493 was applied (Bodurov et al. 2016). Since the ready-to-use mixtures (APP117 and APP123) contained i.a. dibasic calcium phosphate, the refractive index of dicalcium phosphate (1.55) was applied for the respective measurements. The x10 quantile and the x50 quantile from the obtained distribution curves were used to describe the particle size. Determination was challenging for the ready-to-use mixture, since they contained further excipients like polymers and stabilizers. All other excipients except the pigments were however soluble and therefore expected not to interfere with the particle size determination. This was especially the case, since the sample was strongly diluted with water before measurement.
Lipo-PEG nano-ocular formulation successfully encapsulates hydrophilic fluconazole and traverses corneal and non-corneal path to reach posterior eye segment
Published in Journal of Drug Targeting, 2021
Shilpa Kakkar, Mandeep Singh, Sankunny Mohan Karuppayil, Jayant S. Raut, Fabrizio Giansanti, Laura Papucci, Nicola Schiavone, T. C. Nag, Nan Gao, Fu-Shin X. Yu, Mohhammad Ramzan, Indu Pal Kaur
SLNs were characterised for morphology using transmission electron microscopy ((TEM), Hitachi, Japan). Particle size (DelsaTM Nano C, Beckman Coulter, Brea, CA), drug assay/total drug content (TDC), entrapment efficiency (EE), and zeta potential of developed SLNs was also determined. Further physicochemical characterisation in terms of Fourier transform infra-red spectrometry ((FTIR), Perkin Elmer, Waltham, MA), differential scanning calorimetry ((DSC); TA Instruments, New Castle, DE), X-ray diffraction ((XRD), PANalytical, EA Almelo, Netherlands) and nuclear magnetic resonance ((NMR), Bruker, Fällanden, Switzerland), spectroscopy was also done. FTIR and XRD studies were conducted on lyophilised samples. pH, osmolarity, and refractive index ((RI) of the FCZ-SLNs was also determined as a measure of ocular comfort. RI was calculated using the formula n = c/v; where n is the refractive index of the medium, c is the velocity of light in vacuum and v is the velocity of light in the medium. Details of characterisation studies are included in the Supplementary data.
Peripheral eye length measurement techniques: a review
Published in Clinical and Experimental Optometry, 2020
Ingrid Ornella Koumbo mekountchou, Fabian Conrad, Padmaja Sankaridurg, Klaus Ehrmann
The calculation of EL is dependent on the refractive index of the medium through which the light travels. As almost all methods for EL measurements are based on optical eye principles, the measured optical length needs to be converted to physical (geometrical) EL. To convert one into the other, the refractive indices along the optical path must be known. The conversion is based on the assumption that a difference in EL between Gullstrand's schematic eye and a measured eye is due to a difference in the vitreous cavity length. However, some techniques use a group refractive index while others take into consideration refractive indices of each medium. Optical EL as measured with optical low coherence reflectometry is converted to geometrical EL by dividing the optical distance of each ocular component (cornea, anterior chamber, lens, vitreous chamber) along the measurement axis by the corresponding refractive index.2003 Meanwhile, partial coherence interferometry technology uses a single average refractive index for the whole eye when calculating the geometric EL from the optical path length; and therefore the optical path length is divided by the mean group refractive index (taken as n = 1.3549) in order to obtain the geometrical length.1991 One would agree, as many researchers suggest, that devices using optical low coherence reflectometry technology have the potential to be more accurate because variations in thickness of individual optical layers can be taken into account.