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Non-Invasive Techniques in Brain Activity Measurement Using Light or Static Magnetic Fields Passing Through the Brain
Published in Shoogo Ueno, Bioimaging, 2020
Biomaterials with characteristic absorbers for near-infrared light (wavelengths 700 to 1500 nm) are hemoglobin (Hb), myoglobin (Mb), and cytochrome oxidase (CytOx) in mitochondria. Absorption spectrum of Hb and Mb is dependent on their oxidation/deoxidation state. Oxidized copper ions in CytOx. absorb near-infrared light, and the absorption spectrum varies depending on the oxidation/reduction state. In NIRS, the oxidation/deoxidation state of the Hb is measured non-invasively by the Beer–Lambert law (absorbance of a certain wavelength is proportional to the concentration and optical path length of the material through which the light is transmitted) using the intensity of the near-infrared light transmitted in the body. Beer–Lambert law holds in a uniform transparent material without scattering, and it can be used approximately in non-uniform substances such as biological tissue. When the light is scattered in the medium, the modified Lambert–Beer law is used (Figure 11.4) (Delpy 1988). The absorbance (A) is defined with the source intensity Io and transmitted intensity I by
Modelling and analysis of skin pigmentation
Published in Ahmad Fadzil Mohamad Hani, Dileep Kumar, Optical Imaging for Biomedical and Clinical Applications, 2017
Ahmad Fadzil Mohamad Hani, Hermawan Nugroho, Norashikin Shamsudin, Suraiya H. Hussein
The Beer–Lambert law relates the absorption of light to the properties of the material through which the light is travelling. The law formulates that there is a logarithmic dependence between the transmission, T, of light through a substance and the product of the absorption coefficient of the substance, α, and the distance the light travels through the material (i.e., the path length), ℓ. The application of Beer–Lambert law and its modification for skin have been reported by Shimada [69,143,144]. This technique uses the spectral distortion induced by multiple scattering via a linearised equation relating the general tissue attenuation to the tissue absorption coefficient, μa. The absorbance, A, is defined from the reflectance, R, of the skin, which is regarded to be a semi-infinite medium.
Pain Assessment Using Near-Infrared Spectroscopy
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Kambiz Pourrezaei, Ahmad Pourshoghi, Zeinab Barati, Issa Zakeri
The modified Beer–Lambert law states that changes in the concentration of light-absorbing components are proportional to changes in light attenuation, divided by the mean optical pathlength and extinction coefficients of the chromophores in the tissue. The mean optical pathlength is a measure of the average distance that light travels between the source and detector after several episodes of scattering and absorption.
Evaluating the effect of antiscalants on membrane biofouling using FTIR and multivariate analysis
Published in Biofouling, 2019
Mohammad Y. Ashfaq, Mohammad A. Al-Ghouti, Hazim Qiblawey, Nabil Zouari
Figure 2 shows the FTIR results of RO membranes exposed to media containing different carbon sources and H. aquamarina as a bacterial strain. A higher similarity among all FTIR spectra and the absence of any peak shifts shows that there was no interaction between the RO membrane and the biofilm layer and thus biofouling did not cause any obvious structural changes on the RO membrane surface. However, through comparison with the negative controls and virgin RO membrane (pure RO membrane surface), a decrease in the percentage transmittance at specific wavenumbers shows that the formation of biofilm increased after the addition of antiscalants. Because the biofilm present on the RO membrane is subjected to IR radiations, the molecules present in the biofilm will absorb the radiation. The amount of radiation absorbed by the molecules is directly proportional to the number of molecules present in the biofilm or the intensity of the biofilm (Wolf et al. 2002). This result can also be explained through Beer-Lambert law, which states that the absorbance is directly proportional to the thickness and concentration of the sample (Stuart, 2004; Salido et al. 2017) as shown in Equation 5:
Improvement of solubility, dissolution and stability profile of artemether solid dispersions and self emulsified solid dispersions by solvent evaporation method
Published in Pharmaceutical Development and Technology, 2018
Muhammad Tayyab Ansari, Muhammad Sohail Arshad, Altaf Hussain, Zeeshan Ahmad
Assay development for artemether, using HPLC (Perkin Elmer, Waltham, MA), required reverse phase C18 columns (4.6 mm × 250 mm, 5 μ) and UV detector recording absorbance at 215 nm wavelength. The mobile phase comprised a mixture of acetonitrile and water (75:25 v/v) at a flow rate of 1 ml min−1. The injection volume was maintained at 20 μl20,21. A calibration curve was established by plotting the area of absorbance peak (recorded from the injection of known quantities of artemether) as a function of concentration (over a range 78–625 μg ml−1) and the data were modeled using a linear regression equation (y = mx + b). A correlation coefficient of 0.9996 indicated that the data are explained using this model. The linear part of the calibration curve infers the samples follow Beer Lambert Law, suggesting that the absorbance (A) of a sample depends on absorptivity coefficient (a), path length (b) and concentration of the analyte (c); A = a(λ) · b · c22. Providing parameters a and b are constant, the absorbance of a sample will be directly proportional to the concentration of drug. This phenomenon is expressed by the linear regression model. This relationship (concentration dependent linear increase for absorbance) is used reliably to determine unknown concentration of drug in samples. The HPLC method was validated according to the guidelines published by ICH. The results of validation parameters are described Table 2.
Nanocomposite thin films for triggerable drug delivery
Published in Expert Opinion on Drug Delivery, 2018
Lorenzo Vannozzi, Veronica Iacovacci, Arianna Menciassi, Leonardo Ricotti
Light-triggered DDSs have been investigated at different wavelengths, corresponding to the absorbing range of sensitive nanofillers [37]. When irradiated, these elements undergo reversible or irreversible structural changes, even dissipating heat through the embedding matrix (Figure 2(c)) [38]. Light is an interesting external stimulus, featured by quick response time and allowing high spatial and temporal controllability. Light-based strategies are divided into three main classes, depending on the wavelength range used to stimulate the responsive target. Electromagnetic radiation wavelength is inversely proportional to radiation energy and directly influences tissue absorbance and thus penetration depth. The ability to deliver energy to a target strongly depends on the radiation wavelength, on the properties of the diffusion medium, and on the distance from the source. This relationship is governed by the Beer–Lambert law, enabling to quantify the light intensity, and thus the delivered power, at the target as: