Effects of (-)-epigallocatechin gallate and quercetin on the activity and structure of α-amylase

Purpose: To investigate the effects of (-)-epigallocatechin gallate (EGCG) and quercetin on the activity and structure of α-amylase. Methods: The inhibitory effects of 7 functional factors were compared by measuring half maximal inhibitory concentration (IC50) values. Lineweaver-Burk plots were used to determine the type of inhibition exerted by EGCG and quercetin against α-amylase. The effect of EGCG and quercetin on the conformation of α-amylase was investigated using fluorescence spectroscopy. Results: Quercetin and EGCG inhibited α-amylase with IC50 values of 1.36 and 0.31 mg/mL, respectively, which were much lower than the IC50 values of the other compounds (puerarin, paeonol, konjac glucomannan and polygonatum odoratum polysaccharide). The Lineweaver−Burk plots indicated that EGCG and quercetin inhibited α-amylase competitively, with ki values of 0.23 and 1.28 mg/mL, respectively. Fluorescence spectroscopy revealed that treatment with EGCG and quercetin led to formation of a loosely-structured hydrophobic hydration layer. Conclusion: This study has unraveled the mechanism underlying the inhibition of α-amylase activity by EGCG and quercetin in vitro. This should make for better understanding of the mechanisms that underlie the antidiabetic effects of EGCG and quercetin in vivo

Time-dependent energetic proton acceleration and scaling laws in ultra-intense laser pulses interactions with thin foils

A two-phase model, where the plasma expansion is an isothermal one when laser irradiates and a following adiabatic one after laser ends, has been proposed to predict the maximum energy of the proton beams induced in the ultra-intense laser-foil interactions. The hot-electron recirculation in the ultra-intense laser-solid interactions has been accounted in and described by the time-dependent hot-electron density continuously in this model. The dilution effect of electron density as electrons recirculate and spread laterally has been considered. With our model, the scaling laws of maximum ion energy have been achieved and the dependence of the scaling coefficients on laser intensity, pulse duration and target thickness have been obtained. Some interesting results have been predicted: the adiabatic expansion is an important process of the ion acceleration and cannot be neglected; the whole acceleration time is about 10-20 times of laser pulse duration; the larger the laser intensity, the more sensitive the maximum ion energy to the change of focus radius, and so on.Comment: 15 pages, 4 figures, submitted to PR

Transformer Volume Reduction: A New Analysis and Design of an SSSA Control Based 20kW High Power Density Wide Range Resonant Converter

Isolated DC/DC converters play a pivotal rolein the realm of power electronics, particularly in the contextof electric vehicle (EV) fast charging. These converters areresponsible for delivering high-voltage direct current toEVs, sourced from a 3-phase power factor correction (PFC)converter, and exhibit compatibility with both low-voltageand high-voltage vehicle batteries. However, in manyinstances, the demand for constant power charging invarious applications results in a significant portion of thetransformer volume, thereby leading to a decrease inconverter power density. This paper presents a newanalysis and design for a converter based on secondaryside semi-active (SSSA) control. This analysis providestheoretical support for transformer volume reduction andpower density increase. It employs SSSA control totransfer stored energy from the transformer to the resonantnetwork during boost operation, even when fs > fr, with theexcitation inductance participating in resonance. Based onthis analysis, the design of a 20kW 650-850V input to300-900V with 66.7A max output prototype is discussed.The objective is to achieve the highest feasible converterpower density. The designed results confirm that the2*PQ6535 (or 1*PQ6549) core can effectively serve the20kW transformer, resulting in an ultra-high power densityof 14.36 kW/L (235 W/in3)