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971.
Sheng-Yuan Zhang Zi-Wei Li Jie Xu Qiu-Ling Chen Min Song Qing-Wen Zhang 《Molecules (Basel, Switzerland)》2021,26(23)
Three novel monoterpenoid indole alkaloids gardflorine A (1), gardflorine B (2), and gardflorine C (3) were isolated from the leaves of Gardneria multiflora. Their structures, including absolute configurations, were established on the basis of spectroscopic methods (MS, UV, IR, 1D and 2D NMR) and circular dichroism experiments. All the compounds were evaluated for their vasorelaxant and acetylcholinesterase (AChE) inhibitory activities. Compound 1 exhibited potent vasorelaxant activity, with an EC50 value of 8.7 μM, and compounds 2 and 3 showed moderate acetylcholinesterase (AChE) inhibitory activities, with IC50 values of 26.8 and 29.2 μM, respectively. 相似文献
972.
Despite of various therapeutic methods for treating ocular hypertension and glaucoma, it still remains the leading cause of irreversible blindness. Intraocular pressure (IOP) lowering is the most effective way to slow disease progression and prevent blindness. Among the ocular hypotensive drugs currently in use, only a couple act on the conventional outflow system, which is the main pathway for aqueous humor outflow and the major lesion site resulting in ocular hypertension. Nitric oxide (NO) is a commendable new class of glaucoma drugs that acts on the conventional outflow pathway. An increasing number of nitric oxide donors have been developed for glaucoma and ocular hypertension treatment. Here, we will review how NO lowers IOP and the types of nitric oxide donors that have been developed. And a brief analysis of the advantages and challenges associated with the application will be made. The literature used in this review is based on Pubmed database search using ‘nitric oxide’ and ‘glaucoma’ as key words. 相似文献
973.
974.
Song Xu Mengyang Li Gerui Pei Xintian Zhao Jianzhi Xu Chuncai Kong Zhimao Yang Tao Yang 《physica status solidi b》2021,258(12):2100417
975.
In this paper, we consider a scenario where the base station (BS) collects time-sensitive data from multiple sensors through time-varying and error-prone channels. We characterize the data freshness at the terminal end through a class of monotone increasing functions related to Age of information (AoI). Our goal is to design an optimal policy to minimize the average age penalty of all sensors in infinite horizon under bandwidth and power constraint. By formulating the scheduling problem into a constrained Markov decision process (CMDP), we reveal the threshold structure for the optimal policy and approximate the optimal decision by solving a truncated linear programming (LP). Finally, a bandwidth-truncated policy is proposed to satisfy both power and bandwidth constraint. Through theoretical analysis and numerical simulations, we prove the proposed policy is asymptotic optimal in the large sensor regime. 相似文献
976.
Brønsted acid-catalyzed inverse-electron demand (IED) aza-Diels-Alder reactions between 2-aza-dienes and ethylene were studied using quantum chemical calculations. The computed activation energy systematically decreases as the basic sites of the diene progressively become protonated. Our activation strain and Kohn-Sham molecular orbital analyses traced the origin of this enhanced reactivity to i) “Pauli-lowering catalysis” for mono-protonated 2-aza-dienes due to the induction of an asynchronous, but still concerted, reaction pathway that reduces the Pauli repulsion between the reactants; and ii) “LUMO-lowering catalysis” for multi-protonated 2-aza-dienes due to their highly stabilized LUMO(s) and more concerted synchronous reaction path that facilitates more efficient orbital overlaps in IED interactions. In all, we illustrate how the novel concept of “Pauli-lowering catalysis” can be overruled by the traditional concept of “LUMO-lowering catalysis” when the degree of LUMO stabilization is extreme as in the case of multi-protonated 2-aza-dienes. 相似文献
977.
Enhui Shen Dr. Xuehua Song Prof. Qibin Chen Mengmeng Zheng Jianqing Bian Prof. Honglai Liu 《ChemElectroChem》2021,8(1):260-269
High-entropy alloy nanoparticles with a thin metal oxide layer, deposited onto hypercrosslinked polymer-based carbon (HCPC), were synthesized through the adsorption of five metal ions in the hypercrosslinked polymers and subsequent in situ reduction of such ions (Fe2+, Co2+, Ni2+, Cu2+ and Sn2+), followed by a carbonization process. The as-prepared composites exhibit an excellent specific capacitance (495.4 F/g at 0.5 A/g in 1 M KOH), a superior cycling stability (94.7 % of initial capacitance after 15000 cycles at 10 A/g), and ultrafast charge transport kinetics (88.9 % fast kinetic capacitance at 200 mV/s). These excellent electrochemical behaviors are attributed to the pseudocapacitance of the metal oxide layer spontaneously formed on the outermost surface of the composite, having a thickness at the nanometer scale. Such findings suggest that this simple strategy, combining multimetallic nanoparticles with porous carbon materials, has promising potential to improve specific capacitance and paves the way to develop both the preparation of high-entropy alloys and supercapacitors with improved performance. 相似文献
978.
Xinqi Zhao Prof. Xiaohong Sun Prof. Ruisong Guo Song Wang Fuyun Li Tingting Li Shuhui Wang Cheng Gong 《ChemElectroChem》2021,8(9):1558-1570
Lithium-sulfur batteries (LSBs) are considered to be promising candidates for next-generation energy storage devices because of high theoretical capacity of 1675 mAh g−1. However, LSBs have failed to be put into practical applications mainly due to their shuttle effect. SnO2 and SnS2 stand out among many metal oxides and sulfides, and are frequently applied to LSBs research given their characteristics of easy preparation and good chemical stability. In particular, SnO2 has a strong chemical adsorption effect on polysulfides through the S−Sn−O chemical bonds; SnS2 can effectively reduce the electrochemical polarization and improve the redox efficiency of polysulfides. This Minireview summarizes and evaluates the latest research progress of SnO2, SnS2, and SnO2/SnS2 heterostructures applied in LSBs including the cathode, separator, and interlayer. The three materials show excellent electrochemical performance and can serve as viable candidates for polysulfide immobilizers to deal with the shuttle effect in LSBs. 相似文献
979.
Dong Yan Xinyan Li Shuhao Xiao Zhenzhe Li Jianyang Jiang Dr. Rui Wu Prof. Jun Song Chen 《ChemElectroChem》2021,8(18):3538-3543
Na3V2(PO4)3 (NVP) is an attractive cathode material for sodium storage because of its NASICON structure with high ionic conductivity and stability. However, its poor electronic conductivity and large volume change have limited its intensive application. Here, we use 1-butanol as a co-solvent to synthesize NVP (bNVP) microparticles with a uniform carbon coating layer. We discovered that butanol can effectively improve the graphitization level of the carbon, giving rise to a much higher electronic conductivity compared to the sample synthesized without butanol (pristine NVP, pNVP). As expected, bNVP demonstrates high reversible capacities of 110.3 mAh g−1 at 1 C, superior high-rate performance of 98 mAh g−1 at 10 C, and enhanced cycling stability of 94 % capacity retention after 3500 cycles at 30 C, which are far better than pNVP, exhibiting great potential for high-power sodium-ion batteries. 相似文献
980.
As versatile materials with elevated mechanical properties, short fibre reinforced composites (SFRCs) are currently used in many applications. To enhance the mechanical properties, e.g. the ductility, or to reduce crack propagation, short fibres are added to a matrix material, such as polymers or concrete. In the case of concrete, for example, the composite might contain additional aggregates as well. Although the addition of fibres improves the mechanical properties in general, it is well‐known that many matrix materials exhibit creep deformations under constant long‐term loads. The contribution at hand discusses a scaled boundary approach to model the inelastic behaviour of SFRCs. To allow for an efficient and automated mesh generation, the scaled boundary finite element method (SBFEM) is used in conjunction with the quadtree/octree decomposition algorithm. Within this framework, the fibres are modelled in a discrete manner, and the mesh of the matrix is generated independently of the fibres. Applying a novel embedding method, the meshes of the matrix and the fibres are combined, which results in a compatible mesh without requiring additional constraints. Furthermore, it is straightforward to combine the discussed techniques with image‐based mesh generation, e.g. based on computed tomography scans. The current contribution presents various 2D and 3D examples illustrating the efficiency and adaptability of the proposed framework. In addition, we present a methodology to incorporate non‐linear constitutive models into the SBFEM. Separate constitutive equations are formulated for the matrix, aggregates, and fibres. Whereas the mechanical behaviour of the aggregates and the fibres can be modelled within the framework of elasticity, one must make use of non‐linear approaches to account for the rate‐dependent inelastic deformation of the matrix under multiaxial stress and deformation states. Overall, this method allows for the simulation of creep in SFRCs, while considering the complex microstructure of these materials in detail. This provides the basis for a realistic estimation of the effect of long‐term loading on SFRC components. 相似文献