Herein, we report a manganese‐catalyzed three‐component coupling of secondary alcohols, primary alcohols and methanol for the synthesis of β,β‐methylated/alkylated secondary alcohols. Using our ...method, a series of 1‐arylethanol, benzyl alcohol derivatives, and methanol undergo sequential coupling efficiently to construct assembled alcohols with high chemoselectivity in moderate to good yields. Mechanistic studies suggest that the reaction proceeds via methylation of a benzylated secondary alcohol intermediate to generate the final product.
For the first time, a manganese‐catalyzed three‐component coupling of secondary alcohol, primary alcohol and methanol for the synthesis of β,β‐methylated/alkylated alcohol with high chemoselectivity is presented.
Reactive oxygen species (ROS)‐based cancer therapy, such as photodynamic therapy (PDT), is subject to the hypoxia and overexpressed glutathione (GSH) found in the tumor microenvironment (TME). ...Herein, a novel strategy is reported to continuously and simultaneously regulate tumor hypoxia and reducibility in order to achieve the desired therapeutic effect. To accomplish this, a biocompatible nanoplatform (MnFe2O4@metal–organic framework (MOF)) is developed by integrating a coating of porphyrin‐based MOF as the photosensitizer and manganese ferrite nanoparticle (MnFe2O4) as the nanoenzyme. The synthetic MnFe2O4@MOF nanoplatform exhibits both catalase‐like and glutathione peroxidase‐like activities. Once internalized in the tumor, the nanoplatform can continuously catalyze H2O2 to produce O2 to overcome the tumor hypoxia by cyclic Fenton reaction. Meanwhile, combined with the Fenton reaction, MnFe2O4@MOF is able to persistently consume GSH in the presence of H2O2, which decreases the depletion of ROS upon laser irradiation during PDT and achieves better therapeutic efficacy in vitro and in vivo. Moreover, the nanoplatform integrates a treatment modality with magnetic resonance imaging, along with persistent regulation of TME, to promote more precise and effective treatment for future clinical application.
A hydrogen peroxide (H2O2)‐responsive MnFe2O4@MOF nanostructure with continuous auto‐generating oxygen and meanwhile decreasing glutathione capacity in the tumor microenvironment (TME) is developed for enhancing the photodynamic therapy antitumor therapeutic effect. This multifunctional nanoplatform integrating treatment and imaging, along with continuous modulation of TME, could promote more precise and effective treatment in future clinical applications.
In this paper, stabilization for a class of Takagi-Sugeno (T-S) fuzzy memristive neural networks (FMNNs) with mixed time delays is investigated. By virtue of theories of differential equations with ...discontinuous right-hand sides, inequality techniques, and the comparison method, an algebraic criterion is derived to stabilize the addressed FMNNs with bounded discrete and distributed time delays via a designed fuzzy state feedback controller in Filippov's sense. The result can be reinforced to stabilize FMNNs with unbounded discrete time delays. Meanwhile, exponential stabilization of FMNNs with bounded discrete time delays and unbounded continuously distributed delays is also discussed. FMNNs in this study are general since fuzzy logics and hybrid time delays are all considered, and the obtained conditions enhance and extend some existing ones. Finally, four numerical simulations are carried out to substantiate the efficiency and merits of developed theoretical results.
Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation. However, they can ...also display a significant energetic driving force for chemical short-range ordering (SRO). Here, we investigate mechanisms underlying the mobilities of screw and edge dislocations in the body-centered cubic MoNbTaW RHEA over a wide temperature range using extensive molecular dynamics simulations based on a highly-accurate machine-learning interatomic potential. Further, we specifically evaluate how these mechanisms are affected by the presence of SRO. The mobility of edge dislocations is found to be enhanced by the presence of SRO, whereas the rate of double-kink nucleation in the motion of screw dislocations is reduced, although this influence of SRO appears to be attenuated at increasing temperature. Independent of the presence of SRO, a cross-slip locking mechanism is observed for the motion of screws, which provides for extra strengthening for refractory high-entropy alloy system.
This paper investigates the synchronization issue of coupled reaction-diffusion neural networks with directed topology via an adaptive approach. Due to the complexity of the network structure and the ...presence of space variables, it is difficult to design proper adaptive strategies on coupling weights to accomplish the synchronous goal. Under the assumptions of two kinds of special network structures, that is, directed spanning path and directed spanning tree, some novel edge-based adaptive laws, which utilized the local information of node dynamics fully are designed on the coupling weights for reaching synchronization. By constructing appropriate energy function, and utilizing some analytical techniques, several sufficient conditions are given. Finally, some simulation examples are given to verify the effectiveness of the obtained theoretical results.
Fast and strong bio-adhesives are in high demand for many biomedical applications, including closing wounds in surgeries, fixing implantable devices, and haemostasis. However, most strong ...bio-adhesives rely on the instant formation of irreversible covalent crosslinks to provide strong surface binding. Repositioning misplaced adhesives during surgical operations may cause severe secondary damage to tissues. Here, we report hydrogel tapes that can form strong physical interactions with tissues in seconds and gradually form covalent bonds in hours. This timescale-dependent adhesion mechanism allows instant and robust wet adhesion to be combined with fault-tolerant convenient surgical operations. Specifically, inspired by the catechol chemistry discovered in mussel foot proteins, we develop an electrical oxidation approach to controllably oxidize catechol to catecholquinone, which reacts slowly with amino groups on the tissue surface. We demonstrate that the tapes show fast and reversible adhesion at the initial stage and ultrastrong adhesion after the formation of covalent linkages over hours for various tissues and electronic devices. Given that the hydrogel tapes are biocompatible, easy to use, and robust for bio-adhesion, we anticipate that they may find broad biomedical and clinical applications.
A novel AIEgen molecular probe (N-3QL) with typical AIE effects, good biocompatibility, lysosome targeting, pH activation, excellent photostability, and high brightness was synthesized using two ...simple synthetic steps. Spectroscopic and cytotoxicity experiments indicate that N-3QL can not only be used for the dynamic monitoring of cancer cell lysosomes, but also for photodynamic therapy (PDT) ablation of cancer cells.
Abstract
The tuning of molecular switches in solid state toward stimuli-responsive materials has attracted more and more attention in recent years. Herein, we report a switchable three-dimensional ...covalent organic framework (3D COF), which can undergo a reversible transformation through a hydroquinone/quinone redox reaction while retaining the crystallinity and porosity. Our results clearly show that the switching process gradually happened through the COF framework, with an almost quantitative conversion yield. In addition, the redox-triggered transformation will form different functional groups on the pore surface and modify the shape of pore channel, which can result in tunable gas separation property. This study strongly demonstrates 3D COFs can provide robust platforms for efficient tuning of molecular switches in solid state. More importantly, switching of these moieties in 3D COFs can remarkably modify the internal pore environment, which will thus enable the resulting materials with interesting stimuli-responsive properties.
This paper focuses on the finite-time stabilization problem for fuzzy spatiotemporal competitive neural networks (FSCNNs) with discrete and distributed delays. First, the differentiable conditions ...for discrete and finite distributed delays in FSCNNs are removed, and the constraints of the kernel function in infinite distributed delays are weakened. Then, a novel partial differential inequality is proposed to handle the spatial diffusions, which relaxes the restriction for symmetric around the origin of the bounded spatial domain. To stabilize FSCNNs within a finite time, a novel control strategy without delay-dependent terms is established. Moreover, different from the existing works, a more succinct Lyapunov functional is constructed, which does not need to include multiple integral type functional terms to eliminate the influence of the hybrid delays. By virtue of the comparison method and inequality techniques, several sufficient criteria are deduced to guarantee the finite-time stabilization of FSCNNs. Finally, simulations are presented to illustrate the feasibility and effectiveness of the theoretical results.
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