This paper is concerned with the global exponential stabilization of memristor-based chaotic neural networks with both time-varying delays and general activation functions. Here, we adopt nonsmooth ...analysis and control theory to handle memristor-based chaotic neural networks with discontinuous right-hand side. In particular, several new sufficient conditions ensuring exponential stabilization of memristor-based chaotic neural networks are obtained via periodically intermittent control. In addition, the proposed results here are easy to verify and they also extend the earlier publications. Finally, numerical simulations illustrate the effectiveness of the obtained results.
This paper investigates the exponential synchronization of coupled memristor-based chaotic neural networks with both time-varying delays and general activation functions. And here, we adopt nonsmooth ...analysis and control theory to handle memristor-based chaotic neural networks with discontinuous right-hand side. In particular, several new criteria ensuring exponential synchronization of two memristor-based chaotic neural networks are obtained via periodically intermittent control. In addition, the new proposed results here are very easy to verify and also complement, extend the earlier publications. Numerical simulations on the chaotic systems are presented to illustrate the effectiveness of the theoretical results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The utilization of curcumin as a nutraceutical in food and supplement products is often limited because of its low water solubility, poor chemical stability, and low oral bioavailability. This study ...examined the impact of pH, storage temperature, and molecular environment on the physical and chemical stability of pure curcumin in aqueous solutions and in oil-in-water emulsions. Unlike naturally occurring curcuminoid mixtures (that contain curcumin, demethoxy-curcumin, and bisdemethoxy-curcumin), pure curcumin was highly unstable to chemical degradation in alkaline aqueous solutions (pH ≥7.0) and tended to crystallize out of aqueous acidic solutions (pH <7). These effects were attributed to changes in the molecular structure of curcumin under different pH conditions. The curcumin crystals formed were relatively large (10–50 μm), which made them prone to rapid sedimentation. The incorporation of curcumin into oil-in-water emulsions (30% MCT, 1 mg curcumin/g MCT, d 32 ≈ 298 nm) improved its water dispersibility and chemical stability. After incubation at 37 °C for 1 month, >85% of curcumin was retained by emulsions stored under acidic conditions (pH <7), whereas 62, 60, and 53% was retained by emulsions stored at pH 7.0, 7.4, and 8.0, respectively. There was little change in the color of curcumin-loaded emulsions when stored under acidic conditions, but their yellow color faded when stored under alkaline conditions. There was no evidence of droplet aggregation or creaming in emulsions stored for 31 days at ambient temperature. These results suggest that emulsion-based delivery systems may be suitable for improving the water dispersibility and chemical stability of curcumin, which would facilitate its application in foods and supplements.
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A novel computational framework for designing metamaterials with negative Poisson’s ratio over a large strain range is presented in this work by combining the density-based topology optimization ...together with a mixed stress/deformation driven nonlinear homogenization method. A measure of Poisson’s ratio based on the macro deformations is proposed, which is further validated through direct numerical simulations. With the consistent optimization formulations based on nonlinear homogenization, auxetic metamaterial designs with respect to different loading orientations and with different unit cell domains are systematically explored. In addition, the extension to multimaterial auxetic metamaterial designs is also considered, and stable optimization formulations are presented to obtain discrete metamaterial topologies under finite strains. Various new auxetic designs are obtained based on the proposed framework. To validate the performance of optimized designs, a multiscale stability analysis is carried out using the Bloch analysis and rank-one convexity check. As demonstrated, short and/or long wavelength instabilities can occur during the loading process, leading to a change of periodicity of the microstructure, which can affect the performance of an optimized design.
•Novel computational framework for design of nonlinear auxetic metamaterials at finite strains is presented.•Nonlinear homogenization at finite strains is consistently incorporated in the density-based topology optimization.•Optimization formulations with single and multiple hyperelastic phases are considered.•New single and multimaterial auxetic metamaterials designs are discovered.•Multiscale micro and macro stability issues are addressed in the context of metamaterials design.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article focuses on fixed-time synchronization(FXS) and fixed-time stabilization(FTS) for discontinuous neural networks(DNNs) with distributed delays. An improved fixed-time stable lemma for ...differential systems is proposed. Then, by using theory of non-smooth analysis and inequality techniques, some novel sufficient results are established to realize FXS and FTS for such DNNs. What is more, unlike feedback controllers used in most of earlier works, FXS and FTS of this article are achieved by constructing new effective event-triggered control(ETC), which conserve control costs and easier to materialize. In the end, examples and comparisons are displayed to corroborate the correctness and advantages of the derived FXS and FTS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this brief, we consider the exponential synchronization of chaotic memristive neural networks with time-varying delays using the Lyapunov functional method and inequality technique. The dynamic ...analysis here employs the theory of differential equations with discontinuous right-hand side as introduced by Filippov. The designing laws in the synchronization of neural networks are proposed via state or output coupling. In addition, the new proposed algebraic criteria are very easy to verify, and they also enrich and improve the earlier publications. Finally, an example is given to show the effectiveness of the obtained results.
In this paper, adaptive synchronization of memristor-based neural networks (MNNs) with time-varying delays is investigated. The dynamical analysis here employs results from the theory of differential ...equations with discontinuous right-hand sides as introduced by Filippov. Sufficient conditions for the global synchronization of MNNs are established with a general adaptive controller. The update gain of the controller can be adjusted to control the synchronization speed. The obtained results complement and improve the previously known results. Finally, numerical simulations are carried out to demonstrate the effectiveness of the obtained results.
Finite-time stability problem has been a hot topic in control and system engineering. This paper deals with the finite-time stabilization issue of memristor-based delayed neural networks (MDNNs) via ...two control approaches. First, in order to realize the stabilization of MDNNs in finite time, a delayed state feedback controller is proposed. Then, a novel adaptive strategy is applied to the delayed controller, and finite-time stabilization of MDNNs can also be achieved by using the adaptive control law. Some easily verified algebraic criteria are derived to ensure the stabilization of MDNNs in finite time, and the estimation of the settling time functional is given. Moreover, several finite-time stability results as our special cases for both memristor-based neural networks (MNNs) without delays and neural networks are given. Finally, three examples are provided for the illustration of the theoretical results.
Oral ingestion of curcumin is claimed to be effective against several diseases, including inflammation and cancer. However, its utilization in food, supplement, and pharmaceutical products is often ...challenging due to its poor water solubility, high chemical instability, and limited oral bioavailability. Emulsion-based delivery systems can be designed to overcome these challenges, but their composition and structure must be optimized to ensure they function appropriately. This study examined the impact of emulsifier type on the formation and stability of curcumin-loaded oil-in-water emulsions: sodium caseinate; Tween 80; quillaja saponin; gum arabic. The effectiveness of these food-grade emulsifiers at forming emulsions by microfluidization was characterized in terms of their surface load, i.e., the mass of emulsifier per unit surface area. The surface loads decreased in the following order: gum arabic (55.3 mg/m2) > > saponins (2.0 mg/m2) > Tween 80 (1.6 mg/m2) > caseinate (1.5 mg/m2), which indicated that much more gum arabic was required to form emulsions than the other emulsifiers. Curcumin-loaded emulsions were then prepared under conditions where there was just enough emulsifier to cover the droplet surfaces (“critical”), and under conditions where there was an excess of emulsifier in the aqueous phase (“excess”). Initially, both critical and excess emulsions were physically stable and had similar appearances. In all emulsions, curcumin degradation during storage occurred more rapidly at pH 7 than at pH 3, and was faster at 55 °C than at 37 °C. The physical and chemical stability of the curcumin-loaded emulsions also depended on emulsifier type. After storage at 55 °C for 15 days, the extent of curcumin degradation decreased in the following order: saponins > > gum arabic ≈ casinate ≈ Tween 80. Moreover, droplet creaming was observed in the critical Tween 80 and saponin emulsions, but not in the other emulsions. These results suggest that saponin accelerated curcumin degradation, possibly due to its ability to promote peroxidation reactions. Emulsifier concentration did not significantly affect curcumin degradation. These results suggest that the physical and chemical stability of curcumin-loaded emulsions is influenced by emulsifier type and level. This information may be useful for formulating emulsion-based delivery systems for curcumin with improved physicochemical and functional properties.
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•O/W emulsions were prepared using “critical” and “excess” emulsifier concentration.•Emulsifier surface load decreased as gum Arabic > > saponins > Tween 80 > caseinate.•High pH (7.0) and elevated temperature (55 °C) caused faster curcumin degradation.•Using excess amount of emulsifier did not reduce curcumin degradation significantly.•Emulsions stabilized by saponins showed the fastest curcumin degradation.
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We report dual-functional hollow gold nanospheres (HAuNS, ∼40-nm diameter) capable of mediating both photothermal ablation of cancer cells and drug release upon near-infrared (NIR) light irradiation. ...As high as 63% DOX by weight (∼1.7 μg DOX/μg Au) could be loaded to polyethylene glycol (PEG)-coated HAuNS since DOX was coated to both the outer and the inner surfaces of HAuNS. Irradiation with NIR laser induced photothermal conversion, which triggered rapid DOX release from DOX-loaded HAuNS. The release of DOX was also pH-dependent, with more DOX released in aqueous solution at lower pH. Significantly greater cell killing was observed when MDA-MB-231 cells incubated with DOX-loaded HAuNS were irradiated with NIR light, attributable to both HAuNS-mediated photothermal ablation and cytotoxicity of released free DOX.
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