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İlhami Gülçin Riad Elias Akçahan Gepdiremen Laurent Boyer 《European Food Research and Technology》2006,223(6):759-767
Fringe tree (Chionanthus virginicus L.), a shrub of the eastern part of America, used as a raw material by pharmaceutical industries for cholagoque, diuretic, tonic and the preparation of homeopathic tinctures. The identification of lignans as major antioxidant components and determination of their antioxidant activities are of considerable interest, because of the role they play in pharmacological actions. The potential antioxidant activity of the lignans such as phillyrin, pinoresinol-β-d-glucoside (PDG) and pinoresinol di-β-d-glucoside (PDDG) from root bark of fringe tree (C. virginicus L.) were examined by different antioxidant tests including; 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH•) scavenging, superoxide anion radical (O2
•-) scavenging, total antioxidant activity by ferric thiocyanate method, reducing activity by Fe3+–Fe2+ transformation, hydrogen peroxide (H2O2) scavenging and ferrous metal (Fe+2) chelating activities. Phillyrin, PDG and PDDG, as antioxidants, neutralized the activities of radicals and inhibited the peroxidation reactions of linoleic acid emulsion. The total antioxidant activity was determined according to the ferric thiocyanate method. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox, which is a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. Phillyrin, PDG and PDDG showed 67.6, 77.3 and 64.2% inhibition on lipid peroxidation of linoleic acid emulsion, respectively, at the concentration of 20 μg/mL. On the other hand, BHA, BHT, α-tocopherol and trolox exhibited 74.4, 71.2, 54.7 and 20.6% inhibition on peroxidation of linoleic acid emulsion, respectively, at the above mentioned concentration. In addition, phillyrin, PDG and PDDG were effective on DPPH•, ABTS•+ and O2
•- scavenging, H2O2 scavenging, total reducing power and metal chelating effect on ferrous ions activities. Also, BHA, BHT, α-tocopherol and trolox were used as references antioxidants for these various antioxidant activities. 相似文献
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Epitaxial Bi2FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material
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Shun Li Bandar AlOtaibi Wei Huang Zetian Mi Nick Serpone Riad Nechache Federico Rosei 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(32):4018-4026
Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi2FeCrO6 multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9–2.1 eV), for visible‐light‐driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to ?1.02 mA cm?2 at a potential of ?0.97 V versus reversible hydrogen electrode is obtained in p‐type Bi2FeCrO6 thin film photocathode grown on SrTiO3 substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi2FeCrO6 thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi2FeCrO6 films. The findings validate the use of multiferroic Bi2FeCrO6 thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. 相似文献
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A technique for the optimization of the iteration (design) parameter of filters used in frequency-domain iterative deconvolution methods is presented. The technique allows the filter optimization to be performed in the frequency-domain instead of the time domain, which translates into tremendous saving of computation time. The technique provides a quantitative measure of the performance of the filter regarding noise reduction and filtration error. Illustrative examples using computer simulation as well as experimental data are given. The demonstrations show that the technique yields reliable results for the deconvolution of signals in the presence of noise 相似文献
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A new multilayered inter satellite-high altitude platform(HAP)system routing algorithm is proposed,which is mainly based on multipath routing to ensure the network reliability.The proposed multipath routing scheme principally relies on splitting the traffic between different paths to make the best utilization of multiple routes.Linear programming is the main method used for multipath selection.The major constraints to the quality of service(QoS)(delay and link utilization)have been taken into account to meet the criteria of the advanced multimedia applications.Due to the effect of link utilization,the system encounters traffic flow oscillation between paths over time,which affects the system performance.Hence,to fix this issue,we propose a cognitive routing algorithm which reacts to the long-term changes of the traffic loads rather than short-term ones.The performance of the proposed routing techniques has been evaluated using appropriate simulation models and implemented by Matlab. 相似文献
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We develop two new continuum contact models for coupled adhesion and friction, and discuss them in the context of existing models proposed in the literature. Our new models are able to describe sliding friction even under tensile normal forces, which seems reasonable for certain adhesion mechanisms. In contrast, existing continuum models for combined adhesion and friction typically include sliding friction only if local contact stresses are compressive. Although such models work well for structures with sufficiently strong local compression, they fail to capture sliding friction for soft and compliant systems (like adhesive pads), for which the resistance to bending is low. This can be overcome with our new models. For further motivation, we additionally present experimental results for the onset of sliding of a smooth glass plate on a smooth elastomer cap under low normal loads. As shown, the findings from these experiments agree well with the results from our models. In this paper we focus on the motivation and derivation of our continuum contact models, and provide a corresponding literature survey. Their implementation in a nonlinear finite element framework as well as the algorithmic treatment of adhesion and friction will be discussed in future work. 相似文献
69.
M-Ali AL-Akhras Shorooq E. Alzoubi Ahmad A. Ahmad Riad Ababneh Ahmad Telfah 《应用聚合物科学杂志》2021,138(5):49757
The permittivity and conductivity relaxation processes of polyethylene oxide (PEO) composite along with potassium hexachloroplatinate (K2PtCl6) electrolytes additive forming PEO/K2PtCl6 complex composite have been investigated. The complex composite has been used as a model for dry-polymer electrolytes (PEs) due to the fact that, the anion is large enough for mimicking the immobilized anion in real dry-polymer electrolytes. Stand-free composite films with 0%, 1%, 3%, and 5% concentrations of K2PtCl6 have been studied using broadband dielectric spectroscopy in the temperatures range from 150 K until 345 K. The microstructural dynamics revealed the α-, β-, and σ-relaxations and their salient spectral characteristics at various concentrations of K2PtCl6 in PEO. The experimental ε” master curves were fitted to HN function for one and/or two relaxation peaks with and without the electrical conductivity contribution in order to investigate the relaxation time (τ), dielectric strengths (Δε), modulus formalism (M”) and the electrical conductivitie (σ). The translational and reorientational degrees of freedom of PEO/K2PtCl6 complex composites are responsible for the relaxation behavior which is predicted to be correlated to the relaxation behavior of the polymer electrolyte below and above the glass transition temperature (Tg). The relaxation time (τ) deduced from β-relaxation follows Arrhenius-like behavior while that deduced from α-relaxation process follows Vogel–Tamman–Fulcher (VTF) behavior. 相似文献
70.
Maning Liu Haichang Zhang Dawit Gedamu Paul Fourmont Heikki Rekola Arto Hiltunen Sylvain G. Cloutier Riad Nechache Arri Priimagi Paola Vivo 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(28)
Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low‐cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next‐generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability. Here, the key synthesis strategies and the tunable optical properties of PNCs are discussed. The photophysical underpinnings of PNCs, in correlation with recent developments of PNC‐based optoelectronic devices, are especially highlighted. The final goal is to outline a theoretical scaffold for the design of high‐performance devices that can at the same time address the commercialization challenges of PNC‐based technology. 相似文献