Modelling and analysis of skin pigmentation
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
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.
Biomedical Applications in Probing Deep Tissue Using Mid-Infrared Supercontinuum Optical Biopsy
Lingyan Shi, Robert R. Alfano in Deep Imaging in Tissue and Biomedical Materials, 2017
In the MIR range, molecular species exhibit fundamental absorption bands with large extinction coefficients thus MIR spectroscopy potentially provides extremely sensitive chemical analysis. A molar extinction coefficient (or molar absorptivity coefficient) is defined by the Beer-Lambert law and is a measure of the relative light absorption of a particular vibrational mode of a molecular species normalized to the molar concentration of the absorbing species. Knowledge of the molar extinction coefficient allows quantification of the amount of the molecular species present. The response to MIR spectroscopy is collected as a spectrum, of the material concerned, which is a plot of intensity of MIR radiation versus wavelength and shows the uptake of radiation intensity at particular wavelengths due to vibrational absorption of the material which is characteristic of the molecular structure of the material.
Instrumentation for Assessing mTBI Events
Mark A. Mentzer in Mild Traumatic Brain Injury, 2020
Once the deformation is read from the kinetics spectrum, several quantities may be extracted, which can be used to further characterize different candidate materials. These parameters are illustrated in Figure 3.7. The principle used is the Beer–Lambert law, which is normally used to determine the concentration dependence C of a solute in a solvent from absorbance data A: A = εlC, where l is path length and ε is the extinction coefficient or molar absorptivity. In our case all material parameters may be assumed fixed, with the path length l being replaced by mass m due to delamination. Thus, the transmittance T is proportional to the variation ion path length or, equivalently, the mass change. Therefore a priori measurement of T(t) versus known m can be used to compute the change of mass: T(t) = εmρ where ρ is the density and t is the observation time.
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:
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.
Related Knowledge Centers
- Absorption
- Transmittance
- Ultraviolet
- Analytical Chemistry
- Visible Spectrum
- Forward Scatter
- Backscatter
- Mass Concentration
- Absorption Cross Section
- Cross Section