A model of the effective low-strain elastic Young’s modulus of multi-layer stacked composites is proposed, which is capable to account for an arbitrary stacked inclusion. Geometrical and discretization-based model results are validated against measured effective Young’s moduli (from 10 up to 40 kPa) on 14 molded silicone specimens embedding a stiff (298 kPa) inclusion with variable size, position, and stacking. Specimens without inclusion represent the muscle, superficial, and epithelium layers in a human vocal fold with Young’s moduli between 4 and 65 kPa. The proposed model allows to predict the influence of a stiff inclusion, mimicking a structural abnormality or pathology somewhere within the vocal fold, on the low-strain effective Young’s modulus. Quantifying the influence of an inclusion or local stiffening on the vocal fold bio-mechanics is a necessary step toward the understanding and mitigation of structural vocal fold pathologies and associated voice disorders.
The antioxidant properties of the natural plant extracts can be resulted from their ability to chelate transition metal ions, especially Fe 2+ and Cu 2+. For example, the complex formation between ferrozine and Fe 2+ can be disturbed by the presence of other complexing agents which cause a decrease in the red colour intensity of complexes. Phenolic compounds from Pandanus extracts (family: Pandanaceae) may consist of dihydroxy groups, which can conjugate transition metals, therefore preventing the metal-induced free radical formation. This study investigates the metal chelating capacity of Pandanus pygmaeus extracts and their column chromatographic fractions. The ferrous ion chelating (FIC) assay was performed to determine the ability of the extracts in chelating ferrous ion. The stock solution was diluted to five concentrations (1-10 000 µg/mL). 500 µL samples at different concentrations were mixed with 100 µL of 0.6 mM ferrous chloride (FeCl 2 ) and 900 µL of methanol (MeOH). Then, the mixtures (1.50 mL) were incubated for 5 minutes at room temperature. Next, 100 µL of 5 mM ferrozine was added, mixed thoroughly and left in the dark for another 10 minutes. The absorbance of the solution was measured spectrophotometrically at 562 nm. The respective solvent used in this bioassay served as a blank control. Ethylene diamine tetraacetate (EDTA) was used as positive control. The percentage inhibition of ferrozine-Fe +2 formations was calculated. In this assay, only the MeOH extract of P. pygmaeus and positive control EDTA exhibited the chelating activity. The absorbance of ferrous and ferrozine complex was decreased dose-dependently, which means that the chelating activity was increased on increasing concentration from 1-10 000 µg/mL. The highest chelating activity of MeOH extract and EDTA is at 10 000 µg/mL with 85.39% and 99.81%, respectively. However, the chelating activity of MeOH extract still can be improved by increasing the concentration. However, compared to positive control of EDTA, IC 50 of MeOH extract was higher than that of EDTA. The smaller the IC 50 value, the higher the metal chelating activity of the compound / extract. This reveals that the MeOH extract is a moderate metal chelating agent as compared to EDTA. On the other hand, the hexane and dichloromethane extracts do not show any chelating activity as IC 50 value could not be determined. The ferrous ion-chelating activity was shown by methanolic extract of P. pygmaeus and positive control EDTA with IC 50 values 2256.50 ± 59.53 µg/mL and 18.35 ± 0.99 and µg/mL, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.